Here I am trying to clean up my Finn M39 stock - I tried applying soft heat to it to raise the grease and oil out of the stock - Well that ain't working, unless you have to sit there and do it for hours -
It takes hours and hours.
It's not an instant gratification type of job.
If you have access to a pizza oven, try setting that at about 170 degrees and leave the stock in there for 3 hours at a time.
Then pull it out, wipe off what comes out and put it back in for another 3 hours.