Illustrator focuses either a fill or a stroke to be set.
We can control the focus with the hardcoded X key, that toggles fill and stroke, but it also requires to know which is active at the moment to know if we should press it.

It’d be faster for professional user to actually force the stroke or the fill to be active, with dedicated absolute keys instead of relative ones.

I’d use something Alt+X and Alt+Shift+X (these are free), or remapped them to something even more simpler.

There is a related request:
Absolute mode that always sets a fill a single click and stroke with the Alt+click/right click
http://illustrator.uservoice.com/forums/333657/suggestions/44104935