James,
with lacquer (dope) if you dry it to fast with heat, it will do just as Randy says, it will skin over, and then trap solvents. this will cause it to shrink out after you sand it, because sanding opens the pores and allows the solvents to escape. Best to build it up with reasonable coats, one in the morning, one in the evening. If you want to help dry it out, best bet is to wait about an hour after you spray it, then lightly scuff the surface open with something like 320, just enough to get a uniform scratch pattern on the surface. In fact, when I used to paint cars with lacquer, we used to break the surface about every hour to facilitate drying. moderate heat, say 80 to 85 degrees wont present problems as long as the heat is surrounding the airframe. If you expose one side to heat, and not the other, you are encouraging warps to occur. I personally never attack a model with a power sander of any sort. its way to hard to control and you will end up making the surface ripple. Better to sand with blocks, by hand. if you have done your woodwork well, its not as bad as it seems. Just work on one part till its done, then move on,, dont jump around or you will get confused and miss things. set a goal, say this evening, I will get the upper outboard wing sanded completely, stay at it till thats done, it will be a motivator that you are "completing" a task each time you work on it.when you get frustrated, STOP, walk away for awhile and then come back when you are fresh. It takes a LOT longer to fix screw ups than it does to simply walk away and come back later