I have a dumb question

Yup!

Ok, I thought so but wan'nt sure. Thank you Bgrigg.

Sorry about the abrupt answer!

Dual action brushes are very interesting. I have the 150 myself. You'll probably find the medium needle will suffice for 95% of your painting. That's all I have. There is a set screw that allows you to pre-set the AB for a certain size. I find I never use it as it doesn't really work over the full size range. But if you are doing thin line work it will help keep you consistant. Get some plastic milk jugs or large pop bottles for practising on, and practice often!

Good Luck!

The spray comes out of the nozzle in a cone shape. Plain old common sense says that the closer you can get to the surface the narrower the line will be. But to do that you have to balance everything else, including how far you pull the trigger back.

Everything is related. How far you can pull the trigger back without blowing paint everywhere is dependant on the pressure you are spraying at, the viscosity of your paint (how much it was thinned), and how far from the surface you are spraying.

I suggest you do a little experimenting with just some water and alcohol. They have different viscosity and are pretty safe for spraying around. Back light it so you can see the spray. Play with the pressure, trigger position and distance from the target and just observe the spray pattern. It's pretty informative and will give you a good idea on how your paint will go down. You obviously then want to progress to some real paint to practice. Just remember too close, too much pressure, thin paint and full paint trigger equals paint everywhere.