Went through this myself a couple of years back. I started out with Kerosene and tooth brushes. Long tedious work.
I talked to Brian and Joe at the SCW and asked their expert opinions on the best and safest way to remove it, yet retain as much original finish and markings as possible. Unfortunately, they told me to use 'Kerosene and Toothbrushes!'
I used a spray bottle to apply the kerosene, let it sit overnight, then attacked it again the next evening after it had softened. The plastic bondo applicators are good, as well as plastic putty knives. I sanded the corners off the putty knives before I started using them just in case the sharp corners might gouge the red oxide. When it got down to a final wiping I again sprayed the area, let it sit a couple of hours and did the final scrub with a soaked shop towel. Took along time but I think the end result was worth the effort.
And BTW, kerosene fumes can be harmful too. Be sure to keep some air circulating at all times!!!!