I mix enough to fill a quart size glass mason jar, in fact I usually have two jars full. I have a couple of old baking pans that I soak the piece in. I use an old chip brush to keep the piece wet if it doesn't fit entirely in the pan. I usually soak for a few minutes. I will let the piece drip into the pan, then I wipe off the excess with a clean soft rag, usually an old T shirt. Once the piece is wiped down, it will dry in 24-36 hours depending on humidity.
When done with the oil, I use a funnel and carefully pour the oil back into the jar.
Make sure you wear rubber gloves or nitrile gloves when using the oil, and be carful with with the used rags. If you leave them in a pile, they can catch on fire, so soak them in a bucket of water, then lay them over an edge of the bucket till dry.