Might sound simple enough, but really, if two elements of the mix isn't seperated enough, seperate them more.
First you gotta come to an understanding of - Is the kick burying the snare och the snare burying the kick?
Solo the kick/snare tracks, if the kick is burying your snare, take a wide bell and drag it down like -12 dB. Then move it around on the frequency and see where the snare comes through the most. This would be the are where the kick is overlapping the snare. Bring the gain up to 0 dB. Then slowly bring it down to where the snare cuts through, and the kick doesn't sound like shit. That's what I do at least when trying to seperate elements of the mix, works fine for me!