Thanks for all your advice. Needle gun is out. A few bits to check out.
If I have to I will make her sound and live with a moonscape, but I want her to look nice. Noticed some holes breaking though in the superstructure paintwork and rust is beginning to show through on the roof which may be a priority. Painted for sale? The T scraper worked really well where the bitumen was very thin or very loose but this stuff is failing under a thick smooth top layer (it is flexing). I will let you know how I get on.
btw agree with PTE equipment I have a full face visor and have to keep cleaning it down due to the bits. Briefly forgot to put on my ear defenders - ouch! luckily no permanent damage, according to the docs, but was inflamation in the ear canal and a period of tinnitus.