If you are removing stains, we usually use stain remover from Lowe's if it's tiny. If you are trying to sanitize it completely or remove a large stain, best thing to do is call a service like Stanley Steamer. We once had a customer spill an orange soda on a mattress in our showroom and they paid for Stanley Steamer to come out and they removed any sign of the spill. It was rather amazing and the total cost was $110.

I agree with Andrew on this one. We actually have tested Resolve upholstery cleaner on pillowtops with a lot of success. just make sure you test a small section of the bed to make sure you are not going to fade or otherwise destroy the fabrics. the other options is, see if your pillowtop is removable. Our products have removable and dry-cleanable covers, and your local dry cleaner might be able to clean the spots for you. keep in mind, this only applies if your cover detaches from the rest of your mattress, via zipper or other means. If your mattress is double sided, or single sided and the cover does not come off, than upholstery cleaners, or worst case, Stanley steamer or similar cleaning companies might be the way to go.

Go with Stanley Steemer, I wouldn't do it yourself, its easy to make it worse