I use Solarez, and used to use D2T and E tex, on wooden baits, to make them harder and stronger, because wood is not hard by itself.
For me, plastic baits are different.
The clear coat is there to protect the paint on a plastic bait, not the bait itself.. The bait is already hard, and water proof. I use two coats of a thin top coat, like a concrete sealer. It protects the paint well enough that it doesn't fail when it gets nicked by rocks, or hooks.
I make mine even tougher, but not any heavier, by using clear nail polish, if I think it needs more protection, and to keep soft plastics from melting the sealer.
I think two coats of D2T would add too much weight to a plastic bait, and kill the action a little.
And, as you said, it is prone to coming off in chunks because it is a glue, first and foremost, and designed to be rigid, at the expense of flexibility, so it is brittle when spread over a surface, instead of filling a small gap for anchoring.