I agree about 2k paint - easy to use, no more difficult to spray to a good finish than cellulose. The only think to watch is that you specify to the supplier "Air dry" for the hardner as they seem to supply by default hardner for a low bake oven system.
With regards metal finish (flakes) thats a nightmare to both spray and match. Its much more than the mix, its down to individual technique when you apply it for the finish match.
The only caution with 2k is that you MUST use either a good carbon filter mask ( and replace the cartridges periodically) or an air fed hood type mask. The spray mist will not kill you in small quantities (straight away) but will give you some serious health problems long term if not treated with great respect and caution. COPD is an awful way to die.
Good to see that you have a decent colour match Peter, there are an incredible number of variants on white. It surprised me when I first took a white object into Jawel and asked them to match the paint and they produced literally dozens of colour swatches to try to match the colour. They did do a fantastic job of the colour match.
I agree about the etch primers - just be careful to read the instructions about maximum times that they can be exposed to air after initial spraying before applying a primer. Leave them too long and the finish still looks OK but the paint starts to flake off months later.
How are you getting on with your new spray gun Peter? Did you get some gun wash and are you finding it easier to glean up the kit afterwards?