I think RSF Spiked is my new go-to-spray.
My phone camera is old and the pictures don't really do justice to the before/after difference in this rental move out. In the 1st pic, the light square shape is where the mattress lay on the bedroom carpet. The soiling was a combination of red clay and the oils, grime, etc brought in by two large indoor/outdoor dogs who slept on the carpet at the foot of the mattress.
The second pic is after prespray with RSF Spiked, quick agitation with Cimex, and rinse. I was
very impressed with the results and ease of cleaning.
.