...I do this outside, in some large plastic tublike container that was cheap at the the Home Depot over in the storage bins aisle. Seriously, the stuff is absorbable through the skin, and you don't want to be breathing the vapors, or doing this without gloves. Oxalic acid concentrates as crystals in the kidneys.

My stuff (cheapest and easiest to apply) for the frame interiors is this stuff, recommended to me by the local frame builder here. Also from Home Depot in the paint department.



Because it's in a spray form (I think it's just a linseed oil base with a propellant), you can spray it through the little red plastic tube into the brazing holes in the seat stays. Otherwise, those can be problematic to oil without a syringe. Takes a day or two to dry, might benefit from a second application if you are OCD.