Well, all I can tell you is what worked for me.
A Corbin saddle because it provides a fairly flat (does not look it but it really is), wide platform to work with. An Airhawk above to 'float' just above the saddle itself so there is no particular point bearing weight but rather my entire butt. Frankly, Airhawks do exactly what they say they will do. As far as coolness, again, Airhawks help a little bit in that area but do not really allow any appreciable air circulation (a little bit between the mesh and the cells of the cushion). Another material, such as beads (Easy Boys! Not those kind of beads!) defeats what an Airhawk does so no advantage there. Finally, no undergarments with any seams you sit on. For riding, I actually use thin, stretchy pants that no human with any dignity would be caught dead in, cut the legs off and use them under pants. Put all of this together and I can spend over 50 hours riding without any particular or specifically located discomfort- no 'hot spots' and no 'bone aches' when done. Not to say that there is no pain, because there is, but there is no more pain in my butt than my legs, ankles or everything else that has an odd combination of numbness and pain. But 8- 10 hours in the saddle is downright comfy actually. Of all the things I mentioned, the Airhawk is the must crucial and useful.
As far as heat itself, the two things I find very helpful are Baker air wings because they can be turned to actually direct air directly onto your chest / abdomen, which works amazingly well to cool all of the body behind the windshield. The other thing is to stand up and cool your butt off about every 10, 15 minutes, and / or sit on the passenger's ledge for a moment or two. You can feel the cooling take effect immediately and it lasts for a few minutes.
Brian
Now that I have your attention. Summer riding on a gel pad + stock seat in 95+ degrees makes for an uncomfortable sensation in the area that I sit upon. What's the real solution as far as undergarments are concerned? Is there a garment that keeps that area moderately comfortable? I'd get a different seat if I could find one with air conditioning... This thread will probably get sideways real fast, let's try and stay on point. My backside will appreciate it.