I am new to painting and know very little about it. I am painting my truck Blitz Black and read on this forum that I should use one part thinner and one part hardener to eight parts John Deere Blitz Black. My problem is that the dealer told me they do not sell the hardener any longer. Can I use a different brand or are hardeners brand specific. I live in New Mexico and will be spraying in low humidity and 70 degree weather. Thanks