Usually I just excuse myself and try to say it again, and if the second attempt fails I say that I can't say it and apologise (is that ironic? It amuses me a little). In general my block is worse with words beginning 'B' 'D' 'P' and 'T'. As for spelling out loud, I *can* do it but the problem letters really need to be forced out. Forcing a repetition of a letter helped a little in the past. I'd probably still be doing it, but there's only so much mocking you can take before you stop making yourself a target.