I like the heatgun method. It is quick, cheap, and lasts a long time.
This is the effect I acheived on my 2000 VW T4 Transporter.
Couple of things to note: It will only work on original surfaces, so any previous repairs with paint will not react the same way. The surface when heated actually becomes liquid for a very short time (≤1 second), so must not be touched with anything during that time, otherwise an imprint will be left.
This method also sorted out the spotting that nothing else seemed to fix. You can see the heat gun used close to the plastic grill with no adverse effect. k