You want the finer material on the rock dust. Ag lime would be a good substitute for oyster shell for the mix I posted up. This would be a better option than the dolomite. Pro-mix is mostly peat and perlite w/ a wetting agent. I'm not sure what you mean by 'base soil'. Buying a bale of peat moss is more economical than the pro-mix. If by base soil you mean something that will work well for seeds/ cuts...try this. 1 gallon peat moss 1 gallon perlite 1/2 gallon EWC 1tbs Ag lime
Sheesh!!!!! Enough with the over thinking! Fukin Stoners!!!!!!! The Pro Mix comes from the people who supply the peat moss. Just saving you some labor. When I started there was only the peat moss, so I had to make everything from scratch. Pro Mix is nothing more than peat moss, perlite, some dolomite, and some other stuff, mixed up for those with no wheelbarrow and shovel. That's all. Keep the dolomite, it's fine. I have a 40lb bag in the garage. I also have a bag of Ag lime AND gypsum. I use all 3. You don't need to, not the first time out. Gypsum does NOT replace lime. Remember that. Wet
Yes, some are certainly far better than others. I would have to know your general location to point you toward something local.
If you're close to the south Appalachians (Blue ridge mountains) this is a great source: http://www.blueridgevermiculture.com/castings.html
http://www.wormpower.net/us/buy/#.VHT_DckhD5c Try here as well, great shit and you can find them pretty cheap at some places. Hope this helps.
Again, no. Rock phosphate is pretty much a one trick pony AFA micro nutes/minerals/essential elements. Rock dust has more than a few. Basalt IIRC, the most. Way too much info to type. Search *rock dust* in this forum and settle in for a read. Wet