Can't comment on them personnally but bodywork is a shit business to be in,so much to go wrong,spiralling material costs,people with a lack of disposable income are certainly not prioritising getting dents and scuffs done on the car.
Tbh you really need a premises as getting a good paint finish at the side of a carlots gonna be nigh on impossible.
You'd be better off IMO just refurbing alloys and taking dents out,stay away from scuffs and scratches as that way round you can't really go wrong as if the dents too bad in the first place then the garage is not going to be too disappointed if it doesn't work out,their taking a gamble after all.
I'm speaking from experience regarding the paintside as I had my own place,it was hideous,really hard game to make money in as there's just so much to go wrong and the job always turns out to be 10X worse than you think!!!
Be very careful of these franchise things as they always promise loads and offer little in my experience.
To judge your target market,which I would say will be mainly 2nd hand dealers,I would spend a morning ringing round them asking on average what they pay to get a dent removed,how often they use the service etc and is it something they'd use in the future.
This was the type of research I never bothered with my business and it cost me dear.
Iirc most traders pay £30 a dent/ding without paint,factor in your fuel and material costs as about 1/2 of that so £15 in your bin,if your like me you'll need about £4/500pw to pay your bills and keep a decent standard of living so that's a lot of regular work.
Could be a tough thing to do in this climate.