Secondary conditioning tips

I used to use the technique of conditioning in a secondary until I popped an infection last year. I haven't been brave enough to do it again since.

I have a 1.045 milk stout that I want to dry hop with cocoa nibs. I'm considering soaking these nibs in vodka to sanitize. But I'm still nervous about baddies getting into the carboy because there is not much alcohol to preserve the beer and there's still going to be about an inch of headspace. What techniques do you guys use to preserve a beer when aging in a carboy?

Start with everything as clean and steril as possible then leave it alone as much as possible. I have never soaked any added ingrediants in vodka before adding to secondary but, many folks do. In over 45 years of brewing I have never had an infection.