Good thread! I'll try to share some of my thoughts about kydex as well, sure
Let's talk about tape on the blade... yeah, that is of course very important step. Masking tape is best, I use TESA brand (popular here in EU, good quality and THICK) and I use 2 layers usually. Sometimes 3 layers (on knives made of more than 0.2" stock). One "trick" that I use is to put final tape coat with thin transparent packing tape. Masking tape is usually not glossy, so when you press hot kydex against the masking tape that creates "micro-texture" on the inner side of the sheath! For most knives it doesn't matter that much but for very fine satin finished blades YES, IT DOES. Glossy & smooth packing tape is very thin (so it doesn't change the thickness of the tape padding in fact) but it leaves the inner side of the sheath mirror-smooth. That is a trick I use on some of the knives.
BTW, these two sheaths I made yesterday and in that case (very very fine satin finish as you can see) I had to use this trick to prevent that finish from scratching.