I like tri-flow - I just wonder about the long term affect - I have stuck knobs on a couple machines too - the triflow wasn't enough - probably didn't penetrate enough yet. I am thinking heat might help. You want to be careful around any plastic - is there dried on oil or rust? some oils dry and are very gummy - you have to remove that gum or nothing will move.
As far as a bucket - that's ok if you plan to re-paint I guess. Muv has a really good video on the sticky at the top of the sewing machine section.
I get the Triflow from sew-classic - one bottle goes all year for me - very much worth the money.