I have 4 triggers - one for each Fan State change - that sets the appropriate buttons using the "INSTEON Actions->Turn On/Off KeypadLinc Buttons" action. You should read the entire FanLinc and KeypadLinc article, but in particular the last 3 paragraphs.
Correct - you just need to execute them once. With Indigo 6, we've added those commands to the "Interfaces->INSTEON/X10 Power Line" submenu so you don't actually have to create an action group - you can just select the specific command you're interested in and execute it interactively.
In fact, I may have added those menus in Indigo 5 - check here: "Plugins->INSTEON Commands" - both of those commands may be there as well so you don't have to make the Action Group.