I have been successfully using Ultimate Acrylic Thinners for Humbrol, Vallejo, AK Interactive, Lifecolor, Com-Art and Tamiya acrylic paints at weathering workshops for several years. I see no reason why they would not work with Railmatch, and I would think that Vallejo thinners would work with Railmatch paints as well. I haven't tried these last two combinations, so can't recommend them, but Ultimate is OK.
https://www.umpretail.com/products/ultimate-airbrush-thinner