My covering videos are helpful, but one aspect I DIDN'T go into was surface prep.

So here are a few tips:

First, Use Ultracote. You'll find that it is much more user-friendly

Second, If you use Ultracote, they recommend that you DO NOT use balsarite or any other heat-activated adhesive

Third, like JustErik said, sand the entire structure (My least-favorite part) but most importantly, get all of the dust off! The way I do this is to hold the part (Like a wing) in one hand while I beat the heck out of it with the other. Obviously try not to break anything, but give it a few good whacks to get most of the loose stuff off. I will often combine this with blowing on it till the room starts to spin.

Next, take a tack cloth (Which you can easily make by spraying a rag with spray adhesive) and wipe the entire surface down. If you use a dark cloth, you will be amazed at how must dust you'll see on it.

One other little trick I do is (And I don't always do this, but in the few times I've done it, I really liked the results) before the final sanding, coat the wood with a mixture of white glue and water. I don't know the exact ratio off the top of my head, but you don't need much glue! It should be very watery. It will dry clear, but the wood fibers will become stiff and sand much easier. It will also leave a VERY smooth surface.

I would advise any of you to try it on a piece of scrap sheeting and see what kind of results you get. I was really impressed. This also works extremely well in those areas where the woodgrain gets "fuzzy" and you just can't sand it smooth.

Try it. You'll like it!