How do you avoid, or cope with, twists in the sheet that form when you unwrap? These twists tend to jam in the jib car as the jib moves across.
You can see the twists I mean in the video at about 2:20. I single hand so rather than "let it fly" and pull in on the new leeward side I let it fly ... Then pull in, then back to the windward side and un-jam ... Then haul in on the leeward ... Then back to windward to un-jam, then back to leeward for the final adjustment. Very inelegant, maddening at times.
Is it technique, or perhaps I need a more slippery jib sheet?
Great question. It's not a matter of a more slippery jib sheet, as you want it to be as grippy as possible for both you and the winch.
Before you even get ready to start un-cleating or unwrapping anything, make sure the tail of your sheet is free to run and you're not standing on it, and it is not kinked or self-knotted on the cockpit floor.
The best way to release, without fouling, is to first take a couple wraps off the winch so that you have the minimum number of wraps on the winch before releasing. In heavy air, if you take 2 wraps out of the original 4 you may not be able to hold the sheet, so maybe you only take one off. In light air, you can take all but the last wrap off and still maintain the jib trim where it is in preparation for release and tacking.
Once you have taken as many wraps as you can off of the winch, stand over the winch, and look down at it from above. Imaging looking straight down the winch hole. Now when you release, you don't toss the line to the side, you PULL UP towards the point you are viewing from. Or put another way, pull the line swiftly straight up and off the winch. This requires a quick tug and let go technique and the line quickly frees itself and tries to run away.
On non-self tailing winches this technique works best as there is little at the top of the winch drum to get in the way of a swift unraveling. This type of unraveling of the winch from above is also how fishing line flies off of a spin-cast reel.
If the winch is a self tailing winch, the self tailing tab/guide at the top can get in the way. On these type of winches I still pull from above, but instead of a perfectly in-line upward pull, I "flip" the line around in an counter-clockwise fashion as I'm pulling up. It's almost the same arm and hand motion as working the winch handle, but you are pulling the line up and away from the winch at the same time.
Give it a go, and happy tacking!