It's a bit late but I want to add that, for the most accurate sample, you're right - you need to get from 1' to 5' and 12' depths. For the top layer, a post-hole digger is perfect, but for the deeper levels, you'll need some
Drilling equipment. This can be a bit of an investment, but it's worth it if you want to get the best results. Make sure to wear protective gear and be careful when you're drilling! You don't wanna get any of that sludge in your eyes. BTW, it sounds like you're doing the right thing by drying out the samples for 2 days before mixing them. Just remember that you'll need to send in two cups of the soil mix.
