Just buy a few tubes or 2 part flexible epoxy, and get a load of small plastic cards to mix small quantities, stirring the 2 beads together with a small HDPE paddle used to mix, apply and clean up the area. Cheap, and you only mix what you need, and the small remainder will be easy to flake off after it has cured if you choose plastics that are not going to bond with the epoxy, like HDPE, PTFE or PET. It generally adheres well to most board resins, and many other plastics, varnishes and almost any metal. As a bonus it stops ferrite cores whistling.