I must disagree with a number of other responses, save for Route62.
My first airbrush was also a Paasche H, so i know the feeling of learning with that airbrush.
First off, i agree with Route62 with regard to air pressure. I would up it well above 15psi. Personally, i now use a double action gravity fed brush, and i spray around 30psi. I use mainly Tamiya or Gunze thinned with their thinners though, which is an alcohol base, so it flashes off pretty quickly.
If you're using the MM enamels, i find you need to really thin them down to flow, and even more so if you are shooting with a Paasche H.
For the type of painting you are doing here, stick with the fine tip (single line indicator).
When you place the needle (that the part that is screwed in place with the set screw) into the holder, try and adjust the tip (that's the other part that screws up and down) so that the opening between the two is in line with the air flow.
This was something i found to be PITA with single actions - you have to wriggle around and adjust the tip until you get the lines you want, then screw it into place.
I started off with this a/b doing free-hand camo on 1/72 aircraft - so you can certainly achieve that on 1/35 armour. It just takes practice.
Keep at it, you'll get there over time.
Best of luck, hope to see some future builds from you.