There are no highs and lows if you use the proper long boards is THE point. They are so good that all of the things that you can detect by hand are addressed. Of course this is not true everywhere, but it sure reduces the need for guide coat considerably.
After all the body work I have done on the cab through 3 different grits inside and out, I have more than half of the rattle can left. Its just not something that's needed that much anymore. If I think there is any lows after using those long longboards, its time to break out another round of high build urethane primer. They are truely amazing for eliminating alot of the guesswork.
