I've used watyl super etch before. It's ok but pretty thin already so a 4l doesn't go very far. Some paints don't like to stick to it also.
I'd steer away.
Go for 2k epoxy. Durapox or whatever ppgs alternative is.
Topcoat.... if going metallic then you need a clear as the topcoat... use 2k, it goes harder.
If base colour then you can use base as the topcoat. Again use 2k, it goes harder.
Gaz