Years ago (probably 25)I used a produce for drywall repair that I can't find. I think it was made by Red-Devil but could have been someone else. This was for repair (actually hiding) small damaged areas. It was a sheet of very thin nylon material with a heat activated adhesive. You cut it to cover a hole and ironed it on. The edges would dissapear as the adhesive melted. Then you just paint it. The edges were thinner than a layer of paint, so it really did hide the hole.
I can't find this product anywhere. The paint store folks have not heard of it.