the bearing should not fall out of the cap. if it does it should be replaced or the cap is oversized. And yes both the bearing and cranks surfaces should be dry to get and accurate reading with plasti gauge. I would do 1 bearing at a time, relube and reinstall before going to the next.
If the pump and main cap surfaces are machined properly, perfectly flat with no gouges deep scratches etc. a gasket should not be required.