I've used two part builds bog quite a bit on gib and not had issues with shrinkage, softness, etc. I just put a bit of the white part on a tray, put a small line of the red part on, and get what I need done ASAP as it dries really quickly like 5 minutes to sanding. Most of the other ones take hours before you can sand them. The price of any of this stuff is trivial compared with the labor.