The boxed products would take up half the space in his luggage, that's a lot of unnecessary cardboard there.I think he could toss out the boxes, put 5 cans in a gallon sized ziploc bag in his luggage and another five in another ziploc bag somewhere else.

Ziploc bags not required for checked luggage but always good when dealing with liquids/aerosols to guard against leaking.

I can't imagine that 10 Rogaine foam cans would be a problem.

The cans kind of look like a small can of hair mousse.