If I used my Golden Acrylics would this work as a primer/sealer/varnish? If not, what do you suggest?
From their website: Matte Mediums
Use as a Translucent Ground
Both Matte Medium and Fluid Matte Medium can be used as translucent grounds, sometimes referred to as “clear” gessoes. They are thin enough to penetrate canvas and other porous substrates easily, and the matting solids provide an adequate “tooth” for additional paint layers. In thin applications both products can appear quite translucent, while darkening the canvas to a small degree.
Would you suppose it should be thinned down with water before applying or should it be applied straight from the bottle you think?
Yes that needs to be added to something else such as another medium to thin. I read somewhere if you thin with water, be careful. Too much can create a haze
This is my experience with this product in the past:
If mixed with paint and water it works well. Paint finish is fairly matte and it adds back the binders needed to offset the distilled water.
At one point, Melissa George was advocating the use of it mixed with your air dry varnish to make the air dry varnish more matte. So I tried that and the finish cured tacky all over. So I ended up going over it with the RebornFX matte varnish from Macpherson’s I was using at the time and that did cut the tacky feel but of course left it less matte. After that experience, I would be hesitant to use this product full strength on vinyl because the vinyl is not porous enough to allow it to cure out without being tacky. I have not tried it as a primer myself but if I were going to I would cut it with a flow medium or something more fluid. Maybe distilled water will work but I would not know the ratio to use without trying it.