I have recently started using WBS, I got a Presto 23 quart PC about 3 months ago. I've just finished off a 10 KG bag of Black & Gold Wild Bird Seed without any contams, (about 30 quart jars worth over 3 batches). It does contain a lot of sunflower seeds and corn. I scoop up and discard 95% of the sunflower seeds, and the corn doesn't seem to cause any problems. I bought some Natures Works parrot mix yesterday, it's got the same components minus the corn, and much less sunflower seeds. It's about 20% more expensive, but made locally. I haven't tried it out yet.
I soak mine for 12-24 hours, drain and rinse 3-4 times, simmer for 25 minutes, drain, steam dry, then dry on old towels, PC for 90 minutes, (starting when I reach 90 PSI).
Last batch was innoculated with grain to grain in a glovebox, my first attempt at G2G. They're 60%+ now after shaking a few days ago. No contams.
My batch of blue oysters colonised this stuff like wild-fire!