In Roll For Shoes you gain a new related skill if you roll all 6's on your dice roll, however you can spend xp from failed rolls (you gain 1 xp per failure):
XP can be used to change a die into a 6 for advancement purposes but not for success purposes.
Does that mean if I roll a 3 and a 2 I can spend 2 xp to get 6 and 6 and a new skill?
As I see it, spending multiple XP for advancement is the primary method of acquiring higher-level skills at all.
It's the way I've played it, and it certainly makes the skills advance more quickly--which makes the game more interesting, because skill acquisition is one of the primary methods of establishing setting details and determining the nature of the plot (such as it may be).
Perhaps more significantly, in my experience the primary function of XP is to keep everyone relatively close to the same "power level." With the ability to spend multiple XP for advancement, those who fail regularly will wind up with higher skills later on--thus reducing the sting of failure and making them less likely to fail so regularly.
