Sorry, it has been a while since I looked at the tutorials and I forgot all that you covered.
Since you brought up chemicals and their availability, I would like to see if you can source small quantities of a chemical that is used to disaggregate shale and mudstone. Many years ago a chemical known as Quatenary -O was used for this purpose. It was of a tarry consistency and had to be dissolved in hot water. Sometimes the fossils were actually boiled in this solution. The shale and mudstones coating fossils would literally fall off the fossils when soaked in this material. The commercial use for this chemical is in laundry detergents as they cause clay particles to disassociate. After this became unavailable, an amateur found another similar material that he sold as Rock Quat. This was a liquid that worked in the same way. This material is also no longer available. One of the U.C. grad students did some work in Germany and found another product there that was cheap and readily available called Rewoquat W3690. The Dry Dredgers tried to help him obtain this material here in the US but found it unavailable except in drum quantities for lots of money. If you are dealing with shales and mudstones these chemicals are close to miracle products. If you can help us obtain this product there would be a lot of happy people.
When the latest edition of the FOSSIL Newsletter comes out, there will be an article by Dry Dredgers Kyle Hartshorn. It is illustrated with my photos of edrioasteroids. All of these fossils except the last one were cleaned by soaking in Quatenary-O with only a little use of a toothbrush.