I need help desperately

I was trying to do a white zenithal highlight. I've watched a handful of YouTube videos about airbrushes, but still need some help. I think I applied too much thinner, or not enough white paint. What psi should I have my compressor at? What size needle should I use (while we're here, what do the different needle sizes do? I said I've watched some videos, but I think I zoned out during the parts that talk about the needles)? Also I'm adding this because I feel like someone is gonna say it, but don't say "experiment and figure it out!" I'll get to that eventually, but right now I just want to know what all you who reply do. Thank you in advance

I was trying to do a white zenithal highlight. I've watched a handful of YouTube videos about airbrushes, but still need some help. I think I applied too much thinner, or not enough white paint. What psi should I have my compressor at? What size needle should I use (while we're here, what do the different needle sizes do? I said I've watched some videos, but I think I zoned out during the parts that talk about the needles)? Also I'm adding this because I feel like someone is gonna say it, but don't say "experiment and figure it out!" I'll get to that eventually, but right now I just want to know what all you who reply do. Thank you in advance