Ultracote changes its "cuttable" character. If you use a low temp trim iron to tack and seal an edge, it is very easy to cut. However, if you turn up the heat (270 or so) then the adhesive gets involved and makes it like chewing shoe leather. For a top quality edge it's best to use a new blade or frequently stropping the edge to keep it from "laying over" and appearing dull. Don't use a blade that has been used to cut material during the contruction phase of the build!

Some like using an Xacto #11 blade as the "pencil" is considered easier to hold and manipulate. Others like a single-edged razor. Your choice - or better - have some of each.

Higley has a nice edge trimming tool - gives you a very nice, consistent 1/8" overlap. It looks a bit like a block plane with vertical slots near the leading edge. There's a single-edged razor blade bolted to the top. The distance between the bottom and the blade gives you the width of the overlap.

BTW - Ultracote has 3 temperature "characters". When you tack it down on low heat you'll notice that the surface is pretty "marbled". The adhesive is activated enough to hold the film in place. It's easily pulled up and repositioned by reapplying the same heat. Then when you want to "tighten" the surface. This can be done with a heat from 270 - 320 (or there abouts). You'll notice that the surface is no longer marbled but a very tight high gloss surface. You can do this with an iron with a sock or a heat gun. So, what's the 3rd? Stretching heat - 400 or so. This will allow you to hold the iron above the surface of the film (1/16" or more) and allows you to pull and stretch the film over and around curves. It will also allow you to shrink the film (you just don't pull). Just be careful where you lay the iron down - it will melt a bunch of stuff before you know it.