Some do not need to be sized, can be used as cast. Lube can be coated, or just tumble lubed in a plastic bag, and left to dry.
Traditionally, cast bullets were forced through a die, and wax type lube forced into the grooves, but there are other options today.
I have a sizer and size a lot of bullets.
I also have some tumble lube molds that I use because it's just so quick and easy. Plinking loads like WC are no problem.