BTF, if you are only making a small double (3 foot or so) to allow you to do a loop to loop join for your windon leader then the bimini twist is very easy to do by yourself, the main thing is you need soemwhere to sit down and do it. Make a loop about 3 feet long and do 25 turns, then put each of your big toes in the loop and move your feet apart a bit then work the twists up so you can now put your knees inside the loop, then holding the top main line just above the twists in one hand and the tag in the other you spread your knees apart thus tightening up the twists and once enough tension is on then allow the tag end to spiral back down the twists, half hitch one leg of the loop then the other leg and then over both, then to finish off the bimini twist I have a loop of 50lb line about 6 inches long which I lay along the double from the knot back towards the top of the loop (the loop should extend about two inches past the end of the half hitches) then wrap the tag end around the double and the short loop about 5 times and then thread the tag end through the end of the short loop and then pull the short loop back through the line wrapped around the double creating a nice neat knot to finish the bimini twist off. I can do one in about a minute.
The other thing I do for my game outfits is I will thread on a 8 inch length of 50 pound dacron onto the main line before I make the double and then make the bimini twist so the dacron in in the double, then I will whip the dacron with waxed thread in the middle of the double so that it creates another loop about 4 inches long which I use to create the loop to loop join thus giving the mono in the loop to loop connection a bit more protection