Hi Bill,
I agree that that off-brand sandpaper doesn't hold up and is a lousy value.
Automotive sandpaper you mentioned is good for 400+ grit finish for final sanding and paint sanding work but for shaping work I prefer a paper created for woodworking like Klingspor brand paper. Klingspor both outlasts and loads up less than 3M and Norton brand sandpapers by a substantial margin.
My favorite is Klingspor's peel and stick sandpaper rolls in several grits it lasts a looo-ng time and you just peel off the old paper , take the backing off the new paper and stick it on. It is so easy to use, that other papers seem inconvenient, and even though it costs more than regular paper it lasts long enough that is still a good value to me.
In terms of sanding blocks, I use a Tee-bar and I recently bought the "Tadpole" hard rubber blocks used for sanding various rounded surface shapes. I haven't used them a lot yet but they seem handy.
For general sanding, I bought a "3M" sanding block. It has a comfortable knob molded in the black plastic body so it is less tiresome to use than a regular block. One side is rounded and the surface is covered in thin rubber to provide a little cushion for the sandpaper. I like it.
For detail sanding, I cut several lengths of quater-round wood ( used to trim baseboards) and I cover with sand paper. I end up with a flat surface and a curved surface , all in one block, that is useful for detail sanding various parts of the plane. I use peel and stick paper on all these blocks.
I still have several sizes of "Exacto" brand sanding blocks that I use with regular sandpaper.
I am like everybody else in that sometimes you need a special shaped block and I start looking around the house for something that shape that I can get away with borrowing to use as a special "one-off" limited time sanding block.
On second thought, maybe I am not like everyone else, and , that way no other married guy has to "fess-up" to using household items on the sly.
So Bill, I think that covers the sanding blocks I use the most.
Till next time,
Pat Robinson