What should I ask?

I've done some local and I'd strongly advise you do a short ride along before hand and make sure they can shift. My last boss went through 4 13 speed transmissions in a 6 month period trying to find drivers to haul rock, coal, and grain locally. There aren't usually truck stops in local driving so won't have to worry about chatty Cathy's. Your strongest qualities there should be backing skills, shifting skills, and when it comes to the dump beds make sure they can remember to roll the tarp and dump the bags and to be sure it's on flattish solid ground so they don't tip. I've hauled livestock tankers and most everything farm related you can think of and your biggest jackasses are always local drivers because they get used to it and bored and that makes people forgetful enough to not pay attention to plain as day things... like dropping the bed or disengaging the pto or not rolling the tarp before dumping or driving off lol best local drivers generally have been driving local for a while and not job hopping. As far as them knowing the specific equipment ask specific questions or have them a ride along ready for the first few days or you'll have some 30 year old that's been doing it for 50 years and knows it all just breaking stuff