Walnut shell is supposed to be very good.
Unfortunately I have never managed to get my shot blasting equipment to work properly - got several guns and a blasting cabinet, but feel as though throwing the grit at it would be more effective .
Wait a second. What’s with the the thread resurrection.....
The "new" Nitromors without the banned dichloromethane is all but hopeless at removing paint but there is an alternative you can buy.
It's called Starchem Synstryp and can be bought from many places, Ebay included and it is intended for "professional use". It contains the "banned" dichloromethane and is water washable.
Be careful though, it's powerful.
There's another paint stripper produced by Jawel paints but you'll have to go searching for that on line.
I would also ask around at auto paint suppliers to find out what car bodyshops use these days.
Wot he said!
Slop it on big rubber gauntlet gloves ( screwfix cheap) leave it for a good while, agitate with wire brush (use goggles and do it all outside), then hit it with a hose pipe ( do not use a pressure washer you will send it everywhere and trust me its like napalm.It will eat through yer clothes in no time and burn your skin. repeat until done. does not take long and whilst smelly and messy it works and its quick.
You can do a whole car in an afternoon, just need some mates and plenty of stripper.
Rinse and re rinse