Put some thinners through your new gun before you use it, get used to the controls and find your best settings for the job in hand. My gun (cheap HVLP) never goes much over 35psi. Practise on something that doesn't matter (somebody else's car) and keep your speed and distance constant and your gun parallel to the panel when possible. Watch a few videos on youtube, you'll see who's doing it right and who's bodging and read the comments if there are any on the consensus of whether the painter knows what he's doing or not. Get in there and do your best and don't take any notice of critics who have never had a go and keep some thinners and rags handy for when it goes wrong so you can wipe it off before it sets solid.