It's a pain in the backside, but you need to peel the chrome off, flat, spray. Obviously the longevity of the finish depends on prep and paint quality etc.
The chrome surround comes away from the main body of the grill, and you'll need to do this before you start picking away at the chrome. I used a stanley and soldering iron to get at the lugs that hold the two bits together, and once sprayed up used a hot glue gun to rejoin them. What's left of the lugs makes alignment easy.
The worst part of it all is removing the chrome. It takes a while and the peelings are razor sharp. Wear gloves, don't do it where bare feet may follow, and take your time. I used a blade to initially pick away enough to grip with a pair of pliers, then gently peeled it off the plastic. There is a knack to it. Try not to score the plastic under the chrome when you attack it, it just adds more hurdles to the flat and primer process!
I actually think I have a B4 grill somewhere if you need one to have a go.
And thankyou, my Coupe is a beaut, but needs to go soon to make room for the GTI!