Try absolutely smashing your mix with compression (like 10-20db) and see what sticks out/clashes, then adjust. basically it goes that if you can get your mixdown sounding more or less the same with and without compression (bass will disappear when you smash it) you'll have a nicely separated mix which will be much easier to get louder.

running elements that occupy more or less the same frequency ranges through groups and limiting/compressing them (as transparent as you can, you want to see the reduction not hear it) can buy you a few db of headroom and also stop any random peaks from interfering with the rest of your mix. particularly grouping kick and bass can be very effective.