I take mine to a carwash, stand on end in back of truck, pressure wash to clean, then leave standing out in sun on end til dry. Rotate sides occasionally for even drying. After dry, spray with Scotch Guard, let that dry. Wahlah, nice clean mattress.
For cleaning solution, Fabulosa in lavender is my favorite but use your choice of most any low sudsing detergent or cleaner you prefer. Secret is it let it thoroughly dry after cleaning.
This article focuses on dust mites, but is an overall great how-to article on how to clean a mattress. Hope this helps! Hugs, Holly
Baking soda bleach and a little white vinagar in a spray bottle
Once clean, purchase an elasticised padded mattress cover than can be machine washed.