@audiodwebe I'm exactly in same position as you, 3.5+k vinyl and can't figure out how to cull the heard. To sell in large lots not going to happen with me, in the small amount of culling I've done found a few hot stampers worth some real money. So, it seems I need to spend extreme amount of time and effort to go through most of collection and get money's worth, or sell in large lots, lose money.
I also have equal amount of cd's, physical media becomes a burden with time. I have sold cd's in lots of 25 to 30, much easier to get rid of vs vinyl. I still maintain vinyl setup, so l'd like to keep only the best vinyl, the other 2/3rd's could go.
Like the idea of paying someone else to do the grading, take a percentage of sale price. Other than visual grading, not a chance I'm playing all this vinyl on my system, wear and tear on my all tube setup and cartridge. It would be nice to find someone providing such a service.