2K lacquers processing

Hello together, after I’m about to work with 2K paint for the first time and two specialist dealers have proven to be extremely incompetent, I try to get my questions answered here. I want to paint from my oldtimer bonnet and doors. Since I can’t afford a service provider and have access to compressor and spray gun, I want to do this now. So I got from Sikken’s Autocryl Pluss MM paint and now have a Question: I have to touch the paint first with hardener (50%) and dilution (30%). How long is the paint then processable? Since I have to paint three parts, which I cannot spray directly in a row for reasons of space, some time will pass in between. And now I am uncertain whether I should mix all the paint immediately, or always small quantities (which, of course, is rather annoying…). Greeting, jo