The beads used are called "Seed Beads" and are maybe a little less than 1mm wide when placed on edge. I picked up beads in a dozen colors. $2.50 will get you a small tube containing several hundred beads.
I mark each combat platoon with blue green or yellow. Squads get one, two or three beads of the appropriate color. Command stands add a white bead to the mix. HMGs always use red, flamethrowers have an orange bead, and so on. Here are some shots of German infantry with the new base marking scheme.
A German squad with CiC and 2iC leading:

Close up, showing CiC from 2nd squad, a team from second and one from third squad:

Close up showing how the company commander is marked, sample HMG stands:

Group shot of the German infantry company of two platoons (blue and green at top) and four HMG platoons (red, bottom)::
