I used Zero-Rust on my frame also. Reading from a Zero-Rust application guide, "Application with airless spray equipment requires no thinning and can be done directly from the can.
Because Zero-Rust is heavy bodied, thinning is required for siphon gun application. A reduction of 15-20 % with xylene is typical. Recommended thinners are xylene, lacquer thinner, acetone, and acrylic enamel reducer. Do not use mineral spirits or VMP Naptha for thinning. When using a brush or roller, thin to suit."
