firefighter career change into hot shot?

Here's the problem with trying to drive, then have a fire fighters position.
Lets just say you're working a simple 24/48 for the sake of this post.
You work Sunday 24 hrs, get off at 7 am & go to deliver a load 500 miles away. A day over there & a day back, time to unload, eat, get fuel, bathroom two 10 hr breaks, etc, etc.
200 miles from home & you have truck trouble. 3 pm Tuesday afternoon & you're stuck out with a broke truck 200 miles from home. You gotta be on duty at the FD by 7 am Wed morning.
It may not happen often but it will happen.... & more than once. I hope that truck belongs to the chief... he is more likely to be forgiving.

I dont know if you are a driver at the FD, but if so, you wont have to log for driving the fire truck, but you will have to log that driving time on a paper log for the truck driving job. Also, I cant be absolutely certain but, you may have to log all the on duty time from the FD... for the truck driving job.
You are required to log all on duty time & driving time for FMCSA. If not & you have an accident or get caught in an audit that you just came off a 24 hr shift at the FD at 7 AM Monday morning & got into a truck at 7:30 AM, somebody is gonna be in a heap of trouble. You have to be off duty for 10 hours before starting your driving job.... plus, you're gonna have to take a 34 hr reset some where, which is gonna have to be two days off from the driving job every week.

This is just the start of FMCSA rules for you.
(FMCSA = Federal Motor Carrier Safety Administration) They make the rules for trucking.

Good luck my friend....