I’ve stained a lot of veneers using Transtint Dyes dissolved in alcohol, especially curly and quilted Maple. If you try to stain a thin veneer, it will curl or warp as it dries. I mill the veneers I plan to dye fairly thick, about 1/8” or so. I splice them together with superglue and run them through my drum sander using fine sandpaper, 180 or 220 grit, sanding only the side I plan to dye. After dyeing, I allow them to dry thoroughly, then run them through the sander, using 60 grit on the un-dyed surface, to take them down to my desired thickness. I use a 6’ long by 4” wide piece of vertical grained Bamboo flooring as my sled, and I applied self stick drywall sanding sheets to the sled to prevent the lams from sliding while running them though the drum sander. I always dye and mill my veneers first in the building process. That tells my how thick my Bamboo cores should be to attain my desired stack. Works fo me! Richard