The bee would grab "armfulls" of stamens with its rear legs and rub them on its abdomen.

This bee was pollinating on a thistle. I am guessing it is a megachilid from the pollen collectors on the abdomen. The only metallic blue bees I found under Megachilinae in the guide were under Osmiini, but I am probably wrong on both counts. There appeared to only be this single bee at this location, which would fly off and return again a minute or two later.