HumiTape from Humiseal works well for us + the adhesive is silicone free
(Kapton  tape isn't) which is a plus if you're using UR coatings...check out
the HT600 ESD safe version.


From their webpage:

HumiSeal HT500 and HT600: High performance masking tapes will protect finger
contacts, connectors, terminals, unsealed components, etc., from conformal
coatings. Tape is a polyester film with rubber resin and pressure sensitive
adhesive. It is silicone free and contains no chemical release coat. As a
result there is no residue when tape is removed. Available by the roll in a
variety of widths, and as dots, squares and rectangles in a variety of sizes
as well as in custom shapes. HumiSeal HT600 is ESD safe to protect static
sensitive components.


Regards,
Mike Sewell