Well, as a girl who likes anal but needs to be really really turned on to enjoy it...
1. Lots of warming up. The issue for me is not about inhibitions (goodness knows I haven't got many) but being able to relax the anal muscles as anal really hurts otherwise and then I tense even more. Every woman has different things that work for her - but for me I need to be played with and - crucially - to have penetrative vaginal sex for a while until I orgasm. Only then I am able to be open and relaxed enough.
2. Loooots of lube, the type that's recommended for anal is usually quite thick and not as watery. Also, some types (like the ones with glycerine) can burn a bit, so worth checking what works for her.
3. I know that at the point where I've already had an orgasm from vaginal sex, if the guy just pins me down and gets the lube out, then starts putting it on my ass and slowly/gently starts playing with my ass with his fingers while either playing with my clit or fingering me as well, and talking dirty to me about being his little slut and how he's going to fuck my ass like the whore that I am, well I'm pretty much going to be up for anything
4. Start SLOWLY and get her to guide how deep you go in. Stop at points and let her relax around your cock and get comfortable before going deeper. Make sure she uses a vibrator or her fingers to play with her clit as it's soooo good for her and will also make it far less painful and more pleasurable. Or - even better - play with her clit yourself!
5. Remember, you are trying to recreate the intensity you get on coke without the coke as shortcut, so just tease, take time, allow things to build up.
And, p.s. - no way on EARTH I'd let anyone stick anything in my ass if there's a risk of a 2 years old interrupting. Seriously, this is delicate business requiring patience and being relaxed and build up, make sure you only attempt it when he's with grandma.
Have good dirty fun!