If you must shoot JPEG, I'd recommend being conservative with the picture control settings. Clip your blacks or highlights, and you'll never see them again.
Not too much sharpening, low contrast, and not too much saturation on the picture control. This will give you some room if you do need to edit a bit more.
If you are being creative with the picture control, Your tweaking the JPEG in camera and wasting time with that when you could be shooting.
What I've been doing quite a bit lately is shooting RAW, Rating the good shots and Processing them in camera w/ the 5D3. I print 4x6's for 10$ a pop at a photo booth straight from a selphy printer w/ a battery. It works out really well.
Infact, In-camera RAW processing is rapidly becoming my favorite feature on my 5D3!!! Which makes decent prints and a good profit for the occasional photo booth I hold from time to time.