I've not used it for plugs - but I'm sure Mac is right. It is used by artists regularly. Most artist's paint is pretty fragile - so if they use it successfully - I suspect it could be used on plugs without any problem.
I used a similiar product years (30+!) ago on motorcycle tanks. Worked great. New stuff must be wonderful!
He that would make his own liberty secure, must guard even his enemy from oppression; for if he violates this duty, he establishes a precedent that will reach to himself.
Thomas Paine