I decided to freehand the markings on the tanks. After a bit of research to get them (just about) right, I sat down this afternoon and carefully painted them. Yes, there were some errors which had to be corrected.
Once they were all done, I used the airbrush to give both tanks two thin coats of Klear, then a coat of matt varnish. Here is how they looked at that point:
This one uses the markings of an actual tank - "ASP" from 1 Troop of A Squadron, 1st Australian Tank Regiment (the regiment changed names a few times during WW2).
This represents a tank from 7 Troop of B Squadron, 2/6th Armoured Regiment. I couldn't find any information on actual names given to Stuarts, so made one up. I went with B Squadron as they were (with C Squadron) involved in the fighting at Buna and Sanananda.
I decided to take these photos before the tanks got muddied up. I've done that this evening, but the mud effects need to dry overnight before I decided if they need painting or washing.