I use a basic, cheapo lemon reamer. It's a little wooden thing, and I get about a cup of juice from 5 lemons or 4 limes. I'm sure you could find it at the grocery store. (And yes, rolling the fruit helps a LOT.)
I also ream my fruit into a measuring cup over a colander that catches the seeds but lets some of the pulp through. Then I mash the leftover pulp with a spatula to get the juice from it. Works like a charm and it's easy to do while you're trying to get down the SWF.