I hit the local hardware store and picked up some Rust-Oleum Painter's Touch Primer. I get the cans that say "2X Coverage" and have the little icon of two painting cans on it. It sprays on what seems like thicker coats so I always make sure to stay FAR AWAY from the model and do very light, and possibly multiple coats. I started off with black exclusively on tanks when I still played 40k, and have slowly branched out into other colors such as brown and gray.
Lately I have taken it further, which is the reason I decided to post this up. I have been using them almost similar to the army shade products that other companies have produced. I picked up some new colors for my Wife's Daemon army, a VERY colorful army. I grabbed red, light purple, and light pink to use for the different shades of Bloodletters, Daemonettes, and Horrors. These have worked perfectly! I sprayed the models with 2 light coats and my basecoat was already done on the models. She used regular GW washes directly onto this coat and is already starting to get the entire army tabletop ready with very little work.
Here are some images of her first models with the direct spray basecoat and GW washes of her first models.
Fiend conversion sprayed purple, and washed purple.
Bloodletters sprayed red and washed black.
She is taking painting classes at Adepticon this year and is hoping to get the entire army basecoated and then go back and highlight after she learns some new techniques.
Hopefully this showed you some alternate options to help out your hobby. Try out some of these cheap and time saving spray options. They work!