For people I don't want to know about my transition, I am pretty simple.
Me: I am having surgery in X months
Person: What are you having done
Me: Major Abdominal/ Pelvic/ Back/ Chest surgery
Person: Oh whats wrong
Me: I'm having benign growths removed
If they keep asking I get more and more gory. Try talking about incisions, blood, infections etc. Keep droning on about the non-trans specific issues like diet, obsess about constipation, complications of anesthetic and whenever they ask another questions just keep bringing the topic to the most disgusting parts you think of. Most people give up asking they don't want to lose their lunch. Of course if they like gore you could go in the opposite directions and talk about all the forms involved with having surgery. I have had a few who wouldn't back off and I just keep going until they choose to go away. Or you could just say it is private, or fain an anxiety attack and explain that you are too nervous to talk about it.
->-bleeped-<-boy