How often should you remineralize your teeth after bleaching?

Brush 3 times a day. Not sure i understand the question. You can't really actively remineralize the teeth. Things that demineralize the teeth are sugary, acidic foods and drink and acidic plaque. Eat sugary acidic things sparingly, brush 3 times a day with an ada approved Fluoride toothpaste, floss daily, and your teeth should remineralize fine even with bleaching.
It is not necessary. Research has demonstrated that the level of calcium phosphate is not reduced following tooth whitening. However the enamel is porous following the procedure. Therefore you should refrane for eating or drinking anything that would stain a white shirt for about an hour or two.