I have used Brian Toss's tool and similar. I have used stiff wire or tubing to splice double braids up to 12" circumference. But my favorite, at least for up to 5/8" or so is the Samson
fid set. Works really well.
tape. The best, for splicing, because it stretches and compresses, and passes through a line easily.
Scissors. Cutting yarns with a knife pulls them. Scissors whack them off neatly.
Sharpie markers. And a measuring tape.
You will end up making various prickers and openers for splicing, to suit you. Toothbrush handles are a good raw material. Needle gun needles, too. Old screwdrivers.
For splicing 3 strand up to the size of my wrist I don't bother with a fid. But my fingers are pretty strong from doing this my whole life. You will want a couple of different size solid fids and a hollow one or two. You can make hollow fids from pipe. Just cut the pipe with a long taper, maybe 12 to 1, and smooth the edges. Insert and teist, then pass the strand through the hollow to make the tuck. Works really great. I have one I bought at West Marine
that gets lent out a lot.
For wire you will need a proper marlinspike, pliers, a hammer, cable cutters, seizing wire, and pipe wrenches for twisting the wire to help with insertion. A Riggers Screw is a vise designed for splicing wire but for the small stuff we use on sailboats it is neither necessary nor practical.
You may never need to splice wire, but you will certainly splice fiber rope
occasionally. Still, wire splicing skills could come in handy.
There are instructions online for splicing double braid. Look at the Samson
and also the New England Rope
websites and grab the PDF files.
Old double braid is easier to splice if you soak it in fresh water
. A little dish soap helps, too.