The voluntary TDYs bid after everyone else does. If no one bids the ready lines they will be assigned the ready lines (as long as there are enough pilots to bid every reserve line). If a regular person in your base forgets to bid the TDYs will get their bid in before the person who forgot to bid (it usually happens to at least one person a month) If the TDYs are awarded a normal reserve line they will be on the reserve list and proffer based on their seniority. So your best bet is having no one bid the ready lines and have the tdys get them.

As for the ground and sim instructors there are some great ground school instructors (SS) who fly the line regularly. You will get more out of their classes then the professional ground school instructors. (and that's why they are paid 95 hours of CRJ credit a month) There are also some sim instructors and check airmen who have not flown in 15+ years due to losing their medical.