adam bussey

the washing up liquid was the first thing i tried and that didn't work

Fairy power spray does work. You have to completely coat the painted surfaces and leave it overnight, or longer if poss. It doesn't have to be submerged but that helps. It can just be slapped on thick and wrapped up in plastic to keep it from drying out. A scrubbing brush will take the paint off after that. If there are any big bits left, soak again, but tiny little recesses etc will need the paint/sludge scratched or poked out. Look it up on yt

i took the gun completely apart and left the painted parts in a bucket of 95% fairy power spray to 5% water as ian says the after affect is like a sludge. id recommend leaving it in the liquid for at least 24/48 hours for best results