No Tru-oil. Tru-oil is a varnish. The Russians were big fans of varnish, but most other nations did not use it - it was much faster to dip the stocks in a vat of hot oil and let them drain for a while.
Mausers, particularly the ones made in Europe, were treated with raw linseed oil (not boiled).
Check out my thread in the dremel room:
http://www.cotep.org/forum/showthread.php?t=13520
That covers how to rust blue.
Or, if you want, you can send me the pieces and I can do them for you.