Any water based degreaser even palmolive dishwash,the mineral degreasers are better but absorbed by the skin into the liver so be carefull with these.
then sandblast either wet or dry with a cheap sandblast kit or make your own from the popular mechanics homemade 1950 s sandblaster plans on the net.
A needle scaler
,compressed air is a tool worth having also as a lot of dirt has to be scraped off by hand but a sandblaster is quick and real pro leaving an as new finish.
I would do all the donor parts with a sandblaster.
I dont like the latest fad of chemical /electrolitic degreasing for a number of reasons.David