When you open the potion bar as Raze suggest, you can also set a hot key to each potion so you don't have to keep going to the potion bar.
Click on the potion (eg minor health) and press an un-used function key, the key should show up next to the potion (eg as F8).
If you press the function key in-game or when paused, the active character will consume that potion type. You can switch active characters (default key F5) and consume a potion for your next character.
I typically have a hot key set on minor healing, and minor mana.
