Tips on towel training my tiel

We adopted a spunky 8-year-old male cockatiel 2 months ago. I would like to train him to be less fearful of being toweled. He has an old injury on his wing that requires ointment and the whole process of catching him is not fun. I brought a couple of gray towels close to his color. He isn't hand tame, but he happily comes over to eat millet from our fingers. He doesn't spend any time on the floor of the cage (I don't know the history that caused that). Thank you for your experience.