[porridgeraisin]

SRT is a text file with a awk-able format that you can just write a script to update all the timestamps of. There's also a bunch of online services that do it. VLC has it built-in (track synchronisation - you can set delays on video audio and subtitle tracks individually).

[kebsup]

A great thing in VLC are "h" and "k" (I think) shortcuts, which shift the subtitles 100ms forward and backward.