Start taking 1g of sodium nitrate every morning. You'll need a gram scale. You can get it food grade on Amazon. There are many, many studies showing that this harmlessly decreases BP, plus it's good for your riding.
https://trainright.com/nitric-oxide-...c-performance/
I've been doing this for a couple years. It's good.
Never use a mouthwash - it kills the bacteria you need to make NO.