I congrat you for your open mind , for a man of my age 😉, and also for your health.
Give her what she need, and try to found something to learn to her, or be her student, tell her that you inexperienced and want to learn to please and tease her.
Propose her to receive an enema before the scenario, buy a common bulb nr.8, prepare water with baking soda 1.91Oz/Gallon or 55gramms/Gallon or 14gramms/liter the good temperature of water is between 99° and 105°F. or 37° and 41°C. This are very serious values, not coming from an undefined information.
More warm more relaxed, NEVER ABOVE 105°F. or 41°C.
After the enema, rub her ass, turn around, than in the center, like you will shove your finger but don't enter, tease her, once she move her ass to your finger , give her one finger move turn move out wait a while shove in, make love to her ass like you will do it with your cock in her pussy.
After a while try two fingers, never wild, always slow and soft , wild is permitted when both are ready, when she ask it.
Ask her to receive the same treatment as she want receive, AND LEARN, RECORD ALL WHAT IS SHE DOING don't forget any trick, she will fuck your ass, like she want to be fucked.
Buy a big tube of KY, and lube her like you kiss her, enough
ALL the best to you both let the flow and juices be with you.
They are condoms for gays who have more mechanic resistance.
New condoms are quiet resistant.
Arthur