You don't have to give a FP right away. In fact, some compels only get paid out after the scene is done.
So, for those grey areas, wait for the scene to play out, then look back and ask yourself (and the player and the table) 'did your good role-playing sufficiently complicate things?'
If the table agrees, then pay the FP.
If a player is asking for a self-compel, you can always say "sure, go for it and we'll see where it goes", then pay it out after the scene is done.