Unfortunately yellow is a notoriously difficult color to paint in any brand. Paul is correct, lots of thin coats will eventually get the result you're looking for. Washing the kit beforehand is always I good practice, one I often forget to do. I also agree with him on priming. I do it on all my models. I use Stynylrez though. Just a personal preference, Tamiya Fine or Mr. Surfacer 1500 are excellent choices. I do know some very good modelers in my club who do not prime their models at all, but they are using full on Mr. Paint lacquers. That stuff really bites into plastic!
Testors is an enamel paint and is a good all around paint for airbrushing and hand painting. It is very limited in its color range and unless you start mixing it, you will have a hard time coming close to the colors you see on most models here. If that's one of your considerations.
As far as other brands, it seems like there's a new paint line every 6 months these days. It can be quite confusing. I would recommend going to your local hobby store and talking to someone about the lines they carry and how to use each. Some are better for airbrushing than hand painting, and vice-versa.
I have tried a number of brands for both airbrushing and hand painting: PollyS (discontinued), Pactra (discontinued), Aeromaster (discontinued), Testors Model Master (discontinued), Mr. Color (lacquer, formerly called Gunze-Sangyo), Mr. Hobby (acrylic, formerly called Gunze-Sangyo Aqueous), Testors, Mission Models, Tamiya, Mr. Paint Acrylic, AKAN, AK 3rd gen acrylic, the new Humbrol acrylics, Tru-Color, Citadel, Reaper, Lifecolor, Scale Colors, and Vallejo. Personally, I have gone with Vallejo Model Color due to its low odor, local availability, and ease of brush painting, and Scale Colors for their color accuracy in WWII and newer subjects. I accepted the extreme difficulty of airbrushing VMC and that Scale Colors is formulated specifically for airbrushing (although you can brush paint it with patience and effort).
But if I were to recommend one to a beginner, I'd say Tamiya. It is quite common in my area and can be thinned with their acrylic thinner X-20A, their lacquer thinner X-20, water, alcohol, Mr. Leveling Thinner, or straight lacquer thinner. It's probably the best balanced paint between airbrushing and hand brushing. The different colors are very consistent in their viscosity. This makes thinning them much easier. If you have adequate ventilation and protection, Tamiya paint with Mr. Leveling Thinner which is a mild lacquer thinner with retarder, is a very good combination for both airbrushing and hand painting.
Stuart