Here's some pictures of my method of weatherproofing a PL-259 connection. In this situation, it's used on a UHF barrel connector at the top of a sailboat mast. The antenna used is a Larsen PO-150 that simply screws on the top of the barrel connector. I don't recommend using coax-seal. Messy stuff. I use Scotch 2242 rubber tape, Scotch super 33+ vinyl tape and Scotchkote electrical coating. Stretch the rubber tape, sticky side out, tightly around the connection, put on a layer of vinyl tape and then a couple coats of the Scotchkote. It's waterproof, looks professional, and is easily removed by slicing lengthwise with a razor knife and peeling off with no messy residue. The connection will look just as it did when you sealed it. The rubber tape conforms so well that you can easily read any writing that is on the connector embedded in the rubber when you peel it back off again.
This one has been in service for 3 years
Here's the same one after peeling back the tape
Here's another one that has been re-done several times as you can see by the scratch marks of the razor knive on the pl-259.
And here you can see how well the rubber tape conforms to the connection.
And one more showing the writing embedded into the tape.