The idea that climbers do it all the time so you'll be ok is foolish!
Big difference between a dynamic climbing rope and a who knows how old halyard. The climbing rope is designed to stretch the halyard not so much!
For going up a rope I find a kliemheist hitch around a carabiner to be much easier to deal with than a prussic knot
. A pair of ascenders is better.
If I have to go up a siingle halyard I always give it a good hard bounce test a foot or so off the deck. If it holds together with that fall factor I assume it will hold body weight.
A loop around the mast when you get above the spreaders back to your harness will keep you from hitting the deck if something fails. It will hurt and not be fun but better than cratering your deck!
Done smoothly the halyard won't see much above body weight during the ascent.
I use a piece of 8mm hi tech line to go through the thimble on a wire halyard to tie on the climbing rope. Double fisherman on the loop, rewoven 8 on the climbing rope.
I come down on a standard rappel (old ATC or DMM Bug) device on the climbing rope after escaping the system I used to ascend.
I never have anybody winch
me up, that scares the crap out of me! rather do it on fixed lines with muscle power. I trust myself, nobody else when it comes to this.