UKH

Obviously I can't ask for specific adjustments for my bike without you seeing it, but in general how would I change my setup to increase use of gluteal muscles?

I've had a bike fit in the past which didn't really work for me, I know I could try elsewhere but I've been riding for a long while and built maybe 10 bikes (road gravel mtb etc) so am comfortable in changing things myself.

I've done some googling which seems to suggest moving the saddle back and cleats back. 

Saddle back I reckon  

The problem you’ve got is potentially putting strain elsewhere. I’d follow a ‘standard’ set up (plenty of resources online). Ensure you are getting good hip alignment for your level of flexibility. Then target your glutes through adjustments to your spin technique on the bike and additional mobility and activation exercises off the bike. Make small incremental adjustments  based on the feedback your body gives you as you progress if needed.

(Long time keen cyclist with no real formal knowledge on such matters)

IMHO, your cleats need to be where they need to be, which is determined by the shape of your feet.  In my case, that's on a line across the widest part of my foot, with a variation between each one caused by the slightly asymmetrical alignment of my knees/ankles and slightly different-sized feet.  As I'm sure you know, the smallest adjustment here makes a big difference.

Again, IMHO, your saddle position should be determined initially by the dimensions of your bike, including crank length,  so that you are positioned so that your knee alignment with the crank on the drive stroke is right, which is of course modified by your position on your bike.  Hence, if you're in a TT position and riding on the rivet, the saddle would be further forward than if you were sitting up a bit more, because that enables a more powerful circular stroke, assuming that your saddle height is right.

If you move your saddle back, you will reduce your ability to engage your hamstrings and by default use your glutes more.  If you move your saddle back, your shin will move forward to accommodate it. If you move your cleats back, that will push your foot further forward and you'll be in danger of starting to ride a pedalo (well, not really but....) and you will end up using your glutes even more, but only because you knee is too open to use your hamstrings effectively.

So, again IMHO, get your position right for the position you use the most - let's say hands on the hoods and reasonably aero (not pro-aero).  In that position, your saddle and cleats should be right, and should allow you to engage a powerful circular stroke (think bull pawing the ground).  If you get right down on the drops, you should be able to move forward on the saddle a bit to increase the effectiveness of the circular stroke.  If you sit up, you will tend to increase the extent to which you use your glutes, but make it harder to engage your hamstrings.  Grinding uphill should give you a mix of your normal position and the circular motion (circles not pistons), sitting up a bit is more glutes (and when you're knackered this is when you start pedalling squares).  The next one is to master is standing up and 'jogging' easily to give everything else a break  (find a reasonable 8-10 minute hill with a steadyish incline and ride it without sitting down).  Finally full-out honking with a strong down, up and round stroke and a concentration on keeping the 'mill' between your ankles turning powerfully all the way round.

This is all trial and error over the years by me, culminating in a bike fit which changed nothing and induced the bike fitter to ask how I managed to get it right.  The answers were getting the right length cranks and going out with an allen key tucked down my sock and moving things back and forth and up and down a tiny bit at a time and working out what was happening.  You can get used to anything, so each change needs a bit of bedding in, but not too much.  At the end of a longish ride, I'd think about what I had and hadn't been able to do and would make a small adjustment and then see if it made it better.  I changed my shoes recently to summer ones - they are slightly smaller, and as a result  I had to move my saddle a touch forward to keep all the alignment right.

Of course a pro-bike fitter will be along in a moment and say this is a load of nonsense, so take this in the spirit in which it is intended.  I hope that there's something that you can use.

Having said that, I have my saddle as far forward as it will go, frequently migrate to the nose of it especially when pushing hard, and my arse is like a pair of curling stones. 

Saddle too far back and or seat too high can often cause strain at the base of the hamstring and rear of the knee. I think the optimum sweat spot for bike fit is quite precise, especially if you're putting the miles in. 

First time I've seen my method as well. If you can't sit up unaided (a turbo helps) without pressing hard on the bars or tensing every muscle in your abdomen, your saddle is too far forward. Move back until you can just sit up - this balances your weight correctly. Before this, generally locate centrepoint of cleats at 5th metatarsal. Then, fix knee extension with saddle height. Then, re-fix foot position with cleats so you feel a comfortable level of calf flexion (some people prefer to be on their toes) and correct knee angle / float.

Obv, for a TT bike fit, start with the front end cross-section and work backwards to make it the best compromise you can get.

Remember, the bike is adjustable, but the human body is more adaptable. You will change over time and you will change to match your fit - this is part of the confirmation bias of self-fitting. The only way to be sure is long-term training and small adjustments.

I’d agree with several others.  Seat higher or further back BUT as others have also said the bike still needs to fit you.  I think there is a fit circle rather than a perfect fit so as long as you keep within it you’d be o.k.

I say the above because I used to have my seat far far too high and when I was in physio they said I had the strongest glutes they’d ever seen😂😂😂

Cheers

Toby