What upholstery tool do you use?
Staining on mattress can sometime be impossible to remove, I clean mine every 6-12 months some people wait years! You hardly ever see it like you do a carpet and it's so easy just to cover up, out of sight and all that.
I used mpower applied hot and heavy and CFR tool on 400 psi around 1pm, left the window open and the door and it was fully dry by 4-5pm, maybe earlier but I didn't check.
Mpower gives a really great smell as well, make it smell really fresh and clean and not a fake smell like cherry etc.