I'm in Brisbane-aus and couldn't find any suitable soil in bags at the Bunnings here. It all contains wetting agent, mulch and fertilizer. In the end I went to a local landscaping supplier and bought plain top soil. It's grey with a sandy texture and looks like the stuff in the article.
Dolomite should be available at K-mart etc. Why don't you think you should be using the one you bought for orchids?
I'm going to substitute Sulfate of Postash(K2SO4) for the Muriate of Potash(KCl) unless someone can come up with a downside. I've used it previously in my tanks as an ingredient in liquid fertilizer and nothing has died so far
. I can't see why it would cause any harm and the chloride in the KCl won't be providing any benefit while the sulfur can be used by the plants. The Muriate of Potash doesnt seem to be readily available here in any case.
I won't be going nuts with either the dolomite or potash. Just a little sprinkle.