Boiled Linseed Oil. If you go that route you will forfeit the Warmoth Warranty. I have never had a neck fail and they feel like butter finished this way. I only use this on maple necks. Polish sand it with 2000 grit wet/dry sand paper, ( I prefer Klingspor), then take it to your polishing arbor using the Menzera Ultra Fine #3170 polishing compound. After that I hand rub the boiled oil in using my bare hand until it gets so hot from frictiion I can't stand it. Let it set until it completly drys, generally a half hour to and hour on later coats, wipe it down with a clean rag and repeat the process until the wood stops soaking up the oil. Wipe it down good and take it to the arbor for a finlal polish and it will look and feel like glass. I use a separate wheel for necks only since I do not want any oil residue on the wheel that I am final polishing guitar bodies with.
Linseed oil will spontaneously combust on rags so follow the directions on the can for disposal. A quart of oil will last for years. I have lost count of the number of necks that I have done with the quart that I have had for the past 2 years and it is still 2/3 full.
Here is the birdseye neck that will be going on the Oly White that is posted on a different thread. This has been sanded and has had one go on the arbor. Look at the sheen of the wood! It is amazing how well maple polishes up even before it gets oiled. I will oil the back, wet sand and rub out the lacquer on the face and fretboard this weekend and it will be ready to bolt on the guitar.