The only way to move to a server is to move when it's not "Full". Re-populations are usually done weekly, late Monday, sometimes Tuesday (which is different from re-links). But servers will only change in population when there's a massive WvW player shift (guilds disbanding, moving servers, quitting game are prime examples of this). If TC has a link you may want to consider moving there, keeping in mind re-links are every 2 months so you may be moving a lot. It used to be possible to sneak in during dead hours, as you said, but that changed a long long long time ago. Right now, Full is Full.