Mongol,

I think what he means: If the manufaturer says to use 4 parts paint and 1 part hardener then you use 5 parts reducer (thinner). This formula is based on using PPG Concept paint. Other manufacturers have the same kind of 2k urathane paint but may not be as thick as the PPG Concept paint and may not require the same amount of reducer (thinner) to get the same consistency for spraying. I hope this has been helpful.

Larry