Alex Kustov's tips are GREAT! Especially about cleaning, holding and sanding PE.
But I
really don't agree about using an Xacto knife. It's hard to cut in an exact spot (the blade tip slides around on the slippery PE), you have to bear down so hard that the tip of the blade will bend, and it will be dull
after you cut just a few pieces. Even a brand new blade will often just bend the PE instead of cutting it. The very thought of trying to cut PE with an X-acto blade gives me brain warts.
I get excellent results with a small pair of fingernail scissors - the kind with thin, narrow curved blades about 3/4" long. The scissors grip the PE as you cut, so there's no sliding around. You get precisely the cut you want. And because of the curved blade, you can see exactly where the scissor is cutting. And they actually stay sharp!
(Don't waste money on those curved, serrated hobby scissors. They're too thick and they're clumsy to handle. And they can't fit between the narrow spaces on PE sheets.)
Because you can cut so precisely with fingernail scissors, you won't need to spend a lot of time filing off fret material. I use a diamond riffler file for that purpose, and it works beautifully. A few passes and I'm done.
Alex says one thing that can't be repeated too often: "Do not squeeze the part with tweezers, it might slip out and fly away." I'll go a step further and say the part will slip out and fly away. If you're working with small PE items, avoid tweezers! They are the most effective PE propulsion devices ever invented. Use fingers, tape, toothpicks, Blu-Tack, pliers, snot, anything but tweezers.
PE parts hate tweezers, and once they feel their grip, they will fly away and hide. I've spent many humiliating hours on the floor proving this. (I model in 1:43. I know: I'm really asking for this kind of grief.)
I don't want to take away from Alex's tutorial in any way. He offers excellent tips that should be followed - except the one about X-acto blades and PE.
Diddy