Once you've learned the patterns I show above, multiple pill takes are pretty much no-brainers. All you need to do is recognize the pattern and position your block square and tank appropriately. A lot of multiple takes can be done using just a wall as a block square, although it's generally safer to use a friendly pill. I've included a picture gallery of some useful double-takes below; you can see more in the companion maps to this guide, doubles barrage parts one and two.
These double takes are based on: (clockwise from upper left) Psycho Neighbor, Sneaky Bastard, Phallus in Wonderland, Crafty Bastard, Triple Berf, BL's Balls, and Goofball Special.