Plaster of Paris recipe.Add 1 part warm water & 2 parts white glue in mixing bowl. Then add small amounts water, continue to stir. Add water until consistency is smooth & medium thick, (How To Make Clay With Flour)
I use a mixture of gesso and Redi-Filler an all purpose drywall filler for many of my paintings on wood. 3-1 part redi-filler to gesso. I learned this from an art teacher. After, it's completely dry, I sand it down, apply a layer of matte medium, then ready to paint. It's never cracked on me;-)
The effect of this plaster relief technique, when used over an entire wall or room, can be visually stunning. The same technique can be used to repair existing plaster relief or to add interest to boring, flat walls.