I do it when i'm gonna TZ the whole game. only takes a couple seconds to hork a herald. Alt + Tab to swap to Horker, a couple seconds to enter TP and hork, then back to town to wait for the next one.
Only really gets tedious if you want to hork every champion pack you run across. just the herald though is easy.
not worth the time if you're just going game to game doing a single TZ, but getting double herand drops over 15-20 heralds from a full game adds up pretty fast.
Is there a guide to multibox?