Can this be used on my Whirpool GHW9400PTO?
Yes, Affresh washer cleaner W10135699 can be used for your whirlpool washer.
How often should I use affresh?
There is no set time frame of when to use afresh but can be used as often as needed.
Can I use some bleach and Affresh tablet at the same time?
No you would not want to use afresh and bleach at the same time.