Using 5% Lidocaine for Chastity Orgasm Delay

I touched on this earlier today in my Journal post, though it likely didn’t get much attention;) My wife and I have been living full-time in chastity since July 2021. We’ve noticed that during the few times she permits PIV, I reach orgasm VERY quickly. While some aspects of this are desired, she has mentioned wanting me to last longer on occasion. I bought a 5% Lidocaine cream. She also specified that she doesn’t want it getting inside her or causing any loss of sensation for herself. If I place a condom over my penis after applying the cream, will that help? Will I be TOO numb to maintain an erection? When is the best time before intercourse to apply it? How long does its effect last? I know there are many variables involved, but has anyone tried this or have any pointers/suggestions? Thanks!