All of your points are well taken.
My circumstances do not (and as well may be for others) allow for keeping wet lab equipment in the apartment. I do not like the results obtained by even high end labs in the past. Lastly many do not want to make a major investment in equipment, hence the approach suggested for one off slides. Also my experience with a wet lab is that the stuff eventually stinks.

As you are probably aware, a dremel-like device can be run at a slow or very fast speed depending on the specimen. This seems to be useful in preventing picking.
At this time I am satisfied with the initial "flat" cut which is to be mounted on a slide. The final cutter used is a cylindrical rod with impregnated diamonds. I believe at this moment that it will be satisfactory and was not damaged by the "picking" you mention. This still remains to be certain as it was not examined by other than my 10x lens. Aside from this point I still think the roto-tool (in deference to Dremel) can bring the chip to less than a mm with some care of course. And thus be of use for my one-offs. BTW the saws which I have are continuous edge. I hope their thickness will not lead to diamonds being lost and being one off themselves. That may depend on how much pressure is exerted on the saw by the specimen being drawn thru by a weight over a pulley.

Apparently, I was not clear that I was using a jig to hold the slide relative to the roto-tool and the device sets nicely on my kitchen counter within a plastic enclosure to prevent dust etc. Yes the final grinding must be done on a flat glass plate.

I should like to set up an experiment to run the glass below the slides and use a computer program to monitor the transparency to adjust the amount of grit to apply. That may get too messy for me.

I wish I had time to finish this experiment but my efforts are on finishing some geophysical measurement devices.