You can make holes in baked beads larger even if you don't have an electric drill.
Make a pilot thin hole in a bead before baking it. Then enlarge the hole gradually going from smaller to larger drilling bits.
To make it easier to hold a drilling bit, you can fix it in a craft knife instead of a blade; I managed to hold it on its own.
There is just one tip on this technique: after a few experiments I figured out that if you push a drilling bit through the whole bead at once, 4 of 5 beads will crack :)) You have to remove extra clay from inside the bead in small portions. You drill into a bead to a small distance, take out a drilling bit, shake off the clay dust. Then drill a little further into the bead, again take out a drilling bit and shake off the clay. Go this way to the middle of the bead, then do the same going into the bead from the opposite side of a hole.