Mark unfortunately, H1/8010-99-910-6646 has been obsolete for a while. What we need is a Vocabulary of Army Ordnance Stores Section H 1 (a) Paints, dopes & varnishes from the late '50s. I know there was one in 1957, but I only have later incarnations that do not list it.
If a VAOS was found, it very likely would indicate the standard to which it was formulated, this would pre-date DefStans so would most likely be a CS (Chemical Specification) laid down by the Director of Chemical Inspection (CI). This was a branch of the War Office Inspection Organization under the control of the Assistant Master-General of the Ordnance (Inspection) (AMGO (I)).
I have catalogues of Government publications from 1894-1984, although if I eventually found it, there would be little detail other than the title. The chance of unearthing the right CS is remote, not helped by the added confusion that CS Specifications were also issued by the Air Ministry that first appeared in 1936 and relate to Civil Specifications.
I used to use 50 micron aluminium oxide for micro-sandblasting. So that was pretty fine & probably as small a particle as you could easily get. I suppose you could mix some of that in & if it wasn’t giving a noticeable texturing, move onto larger particles.