Hi bob , i use the windsor and newton galeria matt acrylic for my final matt coat and usually thin it a little with distilled water before spraying. I give it a few light coats and leave it for 24 hours before handling, hope this helps , cheers tony
Its just a 'mix it till it looks runny enough' method! One thing though once youve added some water give it a very good stirring , not too vigorously as it can froth up a bit and you dont want loads of bubbles. If its too runny it will spray fine but can separate and go streaky on the model , its just a case of practising on scrap till you get the hang of it, cheers tony
I tried it on my 1/32 MkXVI Tamiya Spitfire and thinned it with water, about 30% for spraying. I found that it worked well but did take a long time to dry and even longer to cure to a hard finish. Much longer than products like AKI Ultra Matt.
I use their matt, and thin 2 parts varnish to 1 of tap water. It would probably go through the airbrush thicker than that, but I find the matt varnish only needs the thinnest misting of a coat to do the job. I love the stuff. Haven't had any problems with slow drying, but would always leave it 24 hours anyway.