Really sorry Michael, I'd just gone on holiday when you posted your question about the asbestos sheeting in June and by the time I got back 2 weeks later the thread had practically disappeared off the radar, such is the speed of activity on this forum. Only saw it when I re-checked the thread today ahead of MOMING on Saturday.
Anyway, excuses aside, the asbestos sheeting was more corrugated cardboard centre, of a larger gauge from that used to do the corrugated iron sheeting. I guess you'd call it regular corrugated card size, in fact. Sprayed it with grey primer and while wet scattered it with a mixture of seived dried sandy soil from my garden. Then when dry applied thin washes of browny-grey acrylic, as close in colour to weathered asbestos cement as I could mix, until it looked about right.