Yep. Personally, I like to use chain lube. It goes on thick, and doesn't shed easily. Wrap a rag in wire. Coat it with it. Push it up the tubes with some dowel, then use the wire to drag it back out. Then use the can and spray it in the end nice and heavy, or repeat the process till your happy.
You can use the aerosol undercoating with the extra long straw the one with the holes in the sides of the straw. That would put a permanent coat inside But don't seal it to good you don't want it to hold water. I would just coat the inside I don't think I would put the plugs in so the water and junk could get out.
I purchased the main frame plugs and the plugs for under the bed off Ebay for about $24. I RTV'd them in and removed the ones Honda installed and RTV'd them too. I didn't spray or put anything in the tubes before installing the plugs. I'm not equipped to spray that long of a distance/deep so thought anything other than oil would/could just hold junk. I never sprayed oil for fear it would not allow my RTV to set up. Having said all this my bike had not been ridden other than blacktop before I installed the plugs.
I put the plugs on every ride so mud doesn't get in the holes. Then I pull them out when washing (after mud is washed off) Then blow dry to get dry. I put the plugs on the seat so I remember to put them in before loading. Just my 2 cents.