How to clean Shih Tzu Ear

[neolihia]

Hi all,
I've recently brought a puppy home (2.5mths) from a home breeder.
Brought him to the vet for first jab last friday and the vet commented that I've not been cleaning the pup's ear. Thus she show me how.
First she use a cotton bud to clean the surface, then stuck the cotton bud into the ear and squeeze the ear. After that pour baby oil onto new cotton bud and do the same. She say that I should do the same every week.

Ever since then, the pup has always been rubbing his ears. I am supposed to bath him tomorrow as it has been a week since his jab and should clean his ears as well. I did some reading on the internet on how to clean/care for shih tzu's ear and almost all website/write-up is say NOT TO use cotton bud.
Can anyone tell me what's the proper way to clean his ears?
Very heart pain to see him scratch his ears like that. Should i bring him back to another vet again to have his ears look at?

Please help.

Thanks