Definitely no spec pay i can tell you that.
Your work depends entirely what base you are at since it is a purple trade.
I'm at an air base so i will tell you what i know.
In GPV (General Purpose Vehicles, so anything from you'd see on the road basically) you'll be doing the daily mail run around the base delivering mail, rations run to the planes giving them their box lunches, Ambulance involves sitting around usually unless theres some emergency and someone needs a ride to the hospital or a plane crashes. Driving VIP's to and fro, Driving bus. Delivering freight with 5 ton.
In Refuelling, you work shift work 2 day 2 eve 2 night 8 hours fuelling the aircraft on base.
in SPV (Special purpose vehicles) dump trucks, graders, loaders, john deer, heavy equipment. You're responsible for maintaining the runway by pulling a sweeper behind you, helping CE with their projects, tractor trailer runs.
Come winter time everyone does SNIC 12hr as the priority is to keep the runways open, and to open up the base.
If you're in an army base it's a whole different story, some people are attached to units that go alongside infantry and others sit around in GPV waiting for something to do, sometimes for days (we do to). I'm sure someone with experience can fill in the army side for me.
The determining factor is what kind of base you're at.
hope that helps