that's the problem with old Siphon feed spray guns,they require 50-60 psi to get the paint to suck up and spray right.

Goody,Just buy a cheap gravity feed spray gun from Harbor Freight, for around $20 you can get one that will do the job and can spray fine with a small compressor like that little 30 gal one mentioned.
The air is only need to make it spray the fluid will come out just be squeezing the trigger with the air not hooked up.That is why they are so effecient and they don't waste paint in the air from alot of overspray as most of the material transfer is on the vehicle.On a gravity feed almost half the cup goes in the air so it cost you twice as much paint to do the job with a siphon as your wasting it.Good paint is not cheap and you don't want to wast it so buy the correct modern type spray guns."GO Gravity or GO Home"

also check out www.tcpglobal.com they can be cheaper then Eastwood and they sell name brand paint plus have and AutoBody store as well which the links are on that site and get any body supplies you need.
Sometimes it is cheaper then driving to the local auto paint supply store and get's shipped to your door and that includes the shipping as the local store inflates their prices.
I was sending all the way to California to get stuff and have it shipped to Florida cheaper then buying at the local supply place which I had an account with and got a discount from regular over the counter customers and the Company I get my custom paints for airbrush was still beating the local store and shipped right to me,no need to waste gas