Personally, I would avoid that "tube method" or any other method that involves forcing the clowns to be hosted. There is a chance of injuring or even having the clown(s) eaten.
IMO/E, time is the best approach. Even with non-natural combos, it has always worked for me, at least 10 different combos (( off the top of my head ))
While an M. doreensis isn't a natural host anemone for ocellaris, they can be hosted by them in our tanks -- have had it happen for me on two different occasions.