For 30 minutes after brushing, nothing, including water, should be in the mouth. This allows fluoride to work. So brushing in the shower is not ideal.

I brush and then wipe my mouth with a paper towel. It is important not to rinse the mouth with water after brushing, again, to let the fluoride do its work.

I also alternate between two kinds of fluoride, sodium fluoride and stannous fluoride. You can buy toothpaste with one or the other OTC, but for sodium fluoride, I use prescription strength toothpaste. My dentist has endorsed my practice of alternating between sodium and stannous fluoride.