Check if behind his ears is red or flaky, if yes you may want to put some moisturizing cream there. If not just normal cleaning with a cloth when you bathe him should be fine
I use baby cotton bud with some baby oil to lubricate the ear. have to be very gentle as their ears are very sensitive and delicate
wet the cotton bud to clean or get a cloth when bath, put soap water and help LO to wipe behind. I do it everyday
just apply some Moisturizer