I use Archer transfers for the stars and the numbers and letters. I've also made my own stencils for US stars, German crosses, and a German unit emblem too. I don't like decals. I quit using them years ago.
For special stuff, try Airbrushler on this forum, he's a sign painter, a tank dude, and he can make stencils for us other tank dudes. I have a project in mind for him, I just need to put the tank back together first.