Unfortunately you can't do upwind sailing in a vacuum.
That being said, you can still use it for the method described in parent post, but you'd still need a different propulsion method to slow you down at the apogee.
So yes, you can produce a sideways component and let gravity do the rest, but that component can never actually push you towards the sun.
The fact that one has a number of force vectors in varying directions with both sailing and solar sailing, both let you work them together in unison get where you want to go.
Quite often when I am "sailing" the wind is light or dies, and I go to "windward" by timing the currents, and wind at best lets me position for the right currents, but below a sufficient level produces no lift to windward.
While I was googling, a couple places likened it to tacking into the wind, but that's a different kind of phenomenon that works because of friction and pressure differences.
(It's been awhile since I've played KSP, I could be wrong.)