Thanks for all the kind words folks!
Had some difficulty last week with casting out a mask, I stupidly forgot to talc down the sculpture before covering it in plaster, which lead to lots of mini airbubbles being trapped in the plaster. Most of them would be easy to snip off the latex, but I was annoyed that I missed that step. The big issue was when I pulled the first cast from the mould and found it was as watertight as a net, with huge airbubbles in the latex as you can see here.
I contacted a friend/mentor to troubleshoot the issue, and it looks like some of the oil based mould release was still on the inside of the plaster mould, causing airbubbles. So i scrubbed the plaster with a chip brush and some lemon juice (citric acid) and then before pouring latex the next time I misted the plaster with water and then used a damp chip brush to brush on a first layer of latex before filling the mould. This turned out much more successful as you can see here.
Here is the mask before trimming the seams.
Most of the problem areas trimmed, still some cleanup to do.
I can use the failed mask pull as a tester for paint etc, hopefully will have an update for you later in the week.
Thanks again!