Steaming Dents Through Finish

[Horsefeather]

I'm working on a 90's Duo-Sonic with the kiddie neck. It's had a rough life and there are lots of dents in the neck. I've successfully steamed dents out before but it has been bare wood. My dilemma here is that I don't really want to have to sand all the poly off this thing to execute this task. I've sanded it down to satin with 400 grit and I'm wondering if the steam trick works through a plastic finish like this at all. Anyone have any experience?