(NSFW) First time anal sex?

My lady wants to experience anal sex. I’ve never done this either and am very reluctant to do anything that might cause her pain or any kind of trauma. She’s showing a great deal of trust in asking me to do this.

I’ve done some research on the basics: plenty of lubrication, start small, very gentle insertion, soft “plugs”, gradually work up to larger diameters.

I’m looking for practical, compassionate advice to make this a pleasurable experience for her.

Should she be trying to relax or strain to accept? What can I do to help her? Is an anesthetic lubricant a good idea? How quickly should we go to larger diameter? Types and material of “trainer” plugs to use?

I’m putting this question in “Social” so people don’t feel constrained, but I’m really looking for serious compassionate answers from those with experience.