set the follow action to last as long as you want the fill to be & point it in the direction of the loop you want to return to. that's basically all there is to it - you don't need to worry about anything after that because its all taken care of by the automatic process set in the launch section (but mind your global quantization).

there's much more to follow actions & launch modes than I have room to cover here, but it's also worth mentioning using them in combination with removed stops & dummy clips (blank clips) will let you launch fills across multiple tracks with the scene launch buttons. notice how quick this is to set up: select the scene, remove stops (which will remove all of them at once), & edit the follow actions (again, changing all the selections at once). with just a few clicks, you can set up multi-clip fills in your set.