It is always best to use the manufacturer brand reducer/thinner for the brand you are using. Everyone has there own mix / brew they use but most have tried various methods and it is what works best for them. As for a thinning ratio, again is a personal choice depending on what you paint. If you need very fine detail you will probably need to go very thin and low pressure, and if detail is not so much a factor then a little thicker and higher pressures. For fine start with around a 10:1 with 5 PSI and work from there, for doing base coats a lot of one color then you can go heavier and higher PSI like 20 to 30. Hope this helps