You can certainly Gardz and prime the walls yourself!
Just make sure to NOT push the Gardz or primer too thin.
Using a top-notch roller cover (I suggest Purdy White-Doves), apply your coats.
The Gardz will go on kinda like skim-milk. It's a little thinner.
Again, when the stabilizing Gardz dries, the patching/skimming/sanding-process can happen.
Don't push a loaded roller-sleeve any farther than 2'x3'!!