..in one word.. GENTLY!
You should not use a q-tip! Heck YOU shouldn't even use a q-tip for your own ears! You can gently wipe their ears with a warm and wet wash cloth.. or wipe with water during bath time too.. ears can clean themselves when being bathed easily.. but just make sure to keep dirt out of them and if you ever notice build up.. clean more regularly!
My husband.. OMG.. biggest wax producer EVER.. so gross! Sometimes he has to go in and have his ears cleaned at the Urgent Care.. I pray Monroe didn't get his "waxy" genes haha