A friend of mine (J0mama) recently showed me something that actually works very well and can save you some time in a pinch.
I love to do sleeving for my wiring but hate having to mess with the connectors (metal) that often times refuse to work a second time once they've been removed, especially small ones like for fans.
A viable alternative for this is to use the liquid electrical tape and simply paint it over the wire coating using a hobby paint brush. This gives it a nice black coating and they actually have two other colors (red and white). It will take 2-3 coats spread thinly but the results are excellent and time saving. I picked up a 4 oz. bottle/118ml for $7.99 at Lowe's which will actually give you plenty of uses.
It's basically plastidip but a little thinner.
This company also offers clear, black, green, red and white.
This is also handy for cutting off end leads or connectors like those for floppy drives that are useless these days.