Non-porous surfaces must be cleaned with toluene or acetone before the sealant is applied.
Smooth the sealant off with a scraper before it cures, being careful not to smooth away so much that it leaves a hollow, then carefully peel off the masking tape, also before the sealant fully cures.
Compatibility testing should be performed prior to use to confirm the suitability of the use of these materials when in contact with each other.