With stickfast, I have had issues with fogginess on the decals from underneath. The ones with the least amount were ones that I let sit for an extra long time (a couple days) before applying the decal. Going over the decal, I'd sort of paint the glue on with a folded paper towel for the first coat just over the decal. Regular application after that.
I went to a hobby store and the guy there said they have a specialty CA that has less off-gassing and will mostly eliminate the need to wait so long. I didn't get any because I haven't done anymore decals since then, so I don't know the brand.