Given that I work over a 500F+ broiler all day in a busy kitchen, I am unfortunately intimately familiar with the issues of swamp ass or monkey ass that lead to chafing.
For preventing, fellas, honestly, Boxer Briefs with a liberal application of good ol' fashioned Corn Starch in the rubbing zones is a great preventative measure.
but, for the extra-tough cases, where a truckload of cornstarch can't prevent, good ol' fashioned Desitin diaper rash ointment is the order of the day.
In my toolbox with all of my knives, whisks, spatulas, and other various kitchen implements, I carry a few necessities:
1 box of Argo Corn Starch, pilfered from the dry goods
1 tube of Desitin
1 can of spray deoderant
1 pint of good dark rum (its for cooking. Yeah, thats it...
) Actually, its a great topical anesthetic, and can lessen the pain of a good cut or burn in other ways
box of bandaids, liquid bandage solution, burn creme, vaseline (works great for protecting new burns and keeping the skin moist so as to lessen scarring.) and neosporin. Also carry some duct tape and electrical tape (electrical is great for closing cuts without sticking too much to the cut), some rubber gloves, some painkillers (a few Advil and some percs for the heavy-duty injuries)
My travel kit carries much of the same gear only I add some q-tips and other niceties.