Brantho-Korrux 3 in 1
Brantho-Korrux 3 in 1 is described as rust preventative paint, primer and top coating, all in one. Because it’s available in just about any RAL colour, it could save some time.
POR-15 (Paint Over Rust)
I’ve used POR-15 for years to prevent or stop rust. The coating is a bit flexible and doesn’t get damaged easily.