Poor, poor Ralph, he has inherited wooly poodle ears. Having owned numerous hairy poodle ears all my life I can recommend Thornit ear powder. Not always easy to find but you will definately get it on ebay. Follow directions, If I've one with bad ears I use it every day for 5 days, then about twice a week until cleared. It's marvellous stuff!!
From experience I prefer powder in poodle ears rather than drops as they clog up the ears, while the powder tends to keep them drier. Because I've always groomed my own poodles their ears are kept plucked and cleaned monthly, but client dogs were usually 6 week intervals. I know as Ralph is poodle cross he may not be at the groomer as often as that so you are probably best to keep on top of his ears yourself.
Thornit is amazing, the dirt just rolls out and ear dries up, also makes plucking easier as you can grip much better. I would say to clients if they can pluck little and often it keeps on top of the growth and is easier on the dog than plucking all in one go.
looks like i need to practise my ear plucking. there is a groomer a short train ride away, so might see if i can et him booked in there once a month or see how much my mobile guy charges just for monthly ear plucking.