Never use a new airbrush on a good model without practicing first on scrap or an old junk model until you get the feel of the new brush. Practice for at least a half hour.
For the sun faded appearance, I either use an offwhite sprayed on the upper surfaces in a very thin "dusted" coat, or mix up a mixture, very thin, of the main color (grey in this case) and flat white. Again, a very thin dusted coat on top of fuselage and top of wings and stab, including over decals. An even lighter coat on upper sides of fuselage, and on sides of rudder and vertical stabs.