Try and use some Bass rosin. Its super sticky and you need 1-3 swipes to get the job done. Thicker strings need more friction.

The sandpaper trick is an old Eddie Van Halen/Les Paul trick. Unfortunately, it's a pain in the ass.

The easier solution is to get yourself some bow rosin. I'd try something like Pop's Upright Bass Rosin.

It's a little softer, and a little stickier than a cello rosin. You'll just need to experiment with it to find out how much you need. You want to be able to adjust your hold, so you don't want to use so much the pick's glued to your fingers.