In the RT leagues, what happens to the usage numbers of someone you drop during the monthly free agent draft?

For example, I have Chris Donnells who, in his 34 PBs, is a stud against righties. I have just about used him up and he has no real carryover value, so I am planning on dropping him this month to pick up someone new. If I, or someone else, picks him up again next month, will he be refreshed? If not, how can you tell who on the free agent lists has been used already and to what extent?

TIA

RobE (Possums)