Agree with Tojo regarding the OD paint. As for the airbrushes, I started out years ago with a cheap single action Testors A/B just to get some experience using one. Once I had a few models under my belt using that thing, I graduated up to a double action unit. But as with all things that you want to excel at, practice practice practice. If you have a "beater" kit, keep it handy to practice painting techniques.
That 109 typically will feature some form of what we call "mottling" - those are the little splotches of paint the Germans applied to the fuselage and rudder areas on many of their aircraft. This can be a difficult technique to master. If you get too close, your splotches are going to look spider-like; too far, not sure what that looks like but it won't be right.
Here are a couple of my earlier attempts at mottling:
Monogram Me109G, built in 1997. 
Monogram Pro-Modeler Me410B Hornisse, built in about the year 2000. 
Here is one where I have built a little more control over the A/B:
Monogram Bf110G-2, built in 2001.
And here is another Bf110 in 1/72 that I did in 2018:
Monogram Bf110E.