Well I only do oral with, and I haven't starved [from lack of work] yet
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I would agree again about the non-latex condoms; I'm allergic so use them anyway but they really make a difference. I only use Skyns but Durex make one called Bare (I think) which I tried once as they were on offer, although I found they tasted vile and just like any other Durex the fit was crap and they were too short. As far as 'normal' condoms go, Mates Natural are good too. The flavoured ones can smell very strong and I've never used them for work - I often wonder how hard it must be for the punter to get the smell off afterwards. You might choke a little on the teat part at first, but it's surprising how quickly you get used to it and it can help desensitise your gag reflex which is good for practising deep throat.
For technique, you've just got to do the usual thing but do it 'harder' - don't be rough or use your teeth, but you need to press a lot more firmly with your lips and tongue and vary your moves a bit, and if you don't mind a bit of licking and sucking around the balls if they're clean and fresh and not sporting an afro, this is often popular IME (and you can ask first to be on the safe side). Of course it feels better without a condom, but then so does shagging and that isn't a good enough reason for me to start doing either of them without. Ditto riding a motorcycle without a helmet - you get the idea
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Whether he's a timewaster or not remains to be seen, but provided he follows your confirmation procedures (and try just ignoring texts/emails) then it shouldn't make any difference - he'll either be there or not, and talk of future bookings is irrelevant. That said, if it's a lot of emails, then it's probably cobblers; I find that these are the ones who tend to cancel at the last minute because they bottle it rather than being TWs per se, and I think a lot of it's down to nerves.