Hi,
As GM, I have sometimes trouble using banes and boons, sigmar's comers and chaos stars in both narration and game mechanics on the level I'd like to. To ease this problem of coming up with stuff on the spot, I started to make charts for each skill check type to document some ideas I could use at the given situation.
Now -- I've only started and most of it is still blank - and I need your ideas! Just keep it flowing freely. What is 3 banes in Stealth check or 4 boons in a Ride check? Of course its highly contextual but some guidelines may be given with enough freedom and flexibility. And these charts would not be restricting and only used by GM when he/she feels fit so they are not part of rules.
Check it out in my house rules set, pages 7-24.