Thanks. I'm going to go with what your using. You seem to know whats up here. I don't paint so I have no clue.
I'll break down a bit more, starting with easiest, cheapest, least toxic, worst results; and then to most difficult, expensive, most toxic, with best results.
Regular alkyd spray paint will get the job done and look good for a while, but take a week or more to fully cure.
Acrylic lacquer spray paint will be harder, adhere better, and cure faster. However, being non-catalyzed, will exhibit minimal chemical resistance.
For a mainstream spray paint , I'd go with an acrylic modified alkyd like Rustoleum Automotive Acrylic Enamel 2X. This technology combines the best properties of acrylic and alkyds.
From here on out there's three choices: epoxy, moisture cured urethane (MCU), and polyurethanes.
Epoxies are very durable, chemical resistant, and adhere extremely well to nearly any type of metal which is why they make excellent primers, but are two-part, UV vulnerable, and are less scuff resistant than polyurethanes. Some are self-etching (such as SPI's) requiring less surface prep for new metal. Some epoxies contain UV inhibitors such as Summit Racing's Chassis Shield. I still wouldn't use it for something that sees significant sunlght.
MCUs such as POR15 are also very durable, chemical resistant, with the advantage of being single-part. However they are generally not usually UV resistant and can be challenging to achieve strong adhesion on smooth metal. POR15 is best used on rough metal or surface rust for proper adhesion. Rust Bullet is a slightly different type of MCU, which claims to be both UV resistant and able to adhere well to smooth surfaces. All MCUs begin to cure upon opening due to air exposure. This gives the entire container a very short shelf life unless the cavity is filled with an inert gas such as argon before sealing the lid for storage.
Polyurethanes exhibit the best UV resistance, chemical resistance, scuff resistance, and finish quality. However, they are relatively expensive, are two-part, should be applied over primer, and contain very toxic isocyanates which require careful use of PPE.
If you'd prefer the best result possible in a can, I'd go with a 2k single use (48hr pot life) spray can like Eastwood AEROSPRAY or SprayMax 2k. Spray Max offers a 2k Epoxy Primer, which if you're not worried about UV resistance on underbody parts, may be sufficient. If you'd like additional protection and best finish, topcoat with Eastwood AEROSPRAY or SprayMax 2k satin polyurethane.
If I had to pick one to use tomorrow, and it had be durable, satin finish, some UV resistance, and not too hard to apply, I'd try Summit's Chassis Shield.
