I have Avast set for manual updates because I'm on a dial up connection, but I know people who have multiple browsers installed and they have no problem getting automatic updates.
As for my configuration, it quite easy to do manual updates, all you do is right click the icon in the system tray (by the clock) and select: Updating, IAVS, and it will perform the update without even opening the Avast AV Program. I have IE6, Opera, and Firefox installed. The update (manually) never takes more than about 20-30 seconds, even on dial up. (but I update daily).
Hope this helps.