I’ve had good luck sealing Epic and Silnylon with both clear GE silicone II caulk thinned with lacquer thinner, and also a Dow Corning product used for sealing circuitry (some electronics shops carry it) called DC-3140. The DC-3140 doesn’t have that vinegar smell as it cures.
I prefer lacquer thinner to mineral spirits as the solvent smell dissipates faster. I generally use 1 part silicone to 2 parts thinner. It takes a bit of mixing to make it homogenous. This is a thin mix that penetrates thread holes well and wicks into thread, though you can’t see it running through.
Sometimes after a leak test fails a second coat is needed, but not often. I apply with a syringe and then use a brush to spread it if necessary. Seam sealing is a PITA but worth it.