IMO, being proactive and being an active part of the action is the way to go with any top, moreso with really hung guys.
In bed (or elsewhere), I'm not into poppers, alcohol, PnP, numbing lotions (i.e. clove oil), etc. Being in control allows you to relax more and not fear what's happening. I prefer to be a participatory bottom, not a scared little victim or a wet rag. If he's not taking the time to relax you and open you up with his fingers, do it yourself. It can be really hot foreplay, especially if you're blowing him at the same time.
Also, since "training" with big toys I've found the confidence to take real monsters. Pre-washing is a must (a couple of hours before play, if washing deeply), again building confidence. The knowledge that you can not only take it, but also keep your composure enough to work him over, in my experience, blows really hung tops away.