It sure sounds unusual to me that you would have trouble getting foams to hook up on asphalt. I used to have my son run rubber tires since they don't chunk like foam. When I drove his car, it never handled well. We have also had some of our better drivers run rubbers to prepare for other races and they usually slow down drastically compared to when they run foam.
Our local asphalt track is also unprepared. The only prep is the groove we lay down as we run. No sugar water or VHT, just raw unsealed asphalt. It is relatively smooth, but not the best. The only changes I make from my carpet setup is to soften the suspension just slightly and run a little more ride height. I have never felt like I didn't have traction. Definitely not as much bite as carpet, but still plenty there.
I run only electric, so that is where my experience is, but the nitro guys also run only foams.