I have only been doing cardstock modeling for a short time, but I have some suggestions that may be worthwhile. I spray the sheet with a solvent base sealer before culling, this seems to eliminate the bleeding thru when the edges are colored. As for coloring the edges, I found that a gray pen or marker is all you need.It looks like a shadow so you don't need a collection of colors. I like to coat the window "glass" with some type of clear gloss. It looks more like glass & breaks up the flat look. I bought 100 # 11 surgical blades w/ a handle from Amazon for $6.75 w/ a handle & free shipping. They seem sharper & are thinner than the regular # 11 blade. They cut extremely well, but go VERY easy on the pressure or you will break the end off. Hope this makes your modeling more enjoyable.....
The tape idea sounds good, could probably even use "Scotch" tape. Just one warning about the surgical blades. They do give you a handle & I recommend that you use pliers when installing them, very easy to slice your hand. My wife was a nurse & she is better at installing the blades than I am, you will understand if you attempt it. Better yet, they will fit in the same handle as the standard # 11 blade. They do bottom out & you could grind some from the end to make them slide in further.
One thing to remember if you are going to use clear tape over the printed windows to simulate glass, DON'T LET IT TOUCH YOUR FINGERS!. My wife hates when I leave fingerprints on the windows.
Charlie
Clark