Whiting Powder is calcium carbonate.
If that is chalk,,I don't know.
Brownells sells it, probably others. Maybe it's available in quantitys from some other industry's use.
A 3lb can lasts a long time.
Most say to mix it into a paste with acetone and paint the slurry onto the stock.
I use cheap rubbing alcohol instead of acetone.
The idea of the acetone is said to draw the oil out of the wood.
The whole idea of this very slow method is to allow the oil to be draw out on it's own and captured in the absorbant whiting powder.
The acetone or alcohol is nothing more than a way of mixing the powder into a paste type consistancy so you can paint & gob it onto the wood where it will stick.
The acetone evaporates in a few seconds anyway, not giving you any advantage over the alcohol which takes a couple of minutes. That at least allows you to add layers of the stuff w/o the previous ones crumbling off.
The coating is very fragile when it dries. Hang the wood in a safe place and leave it alone for a few days. The bright white coating will turn yellow/brown as it draws the oil out of the wood.
When it looks like it's taken about all it can,, hold the wood over a trash can and brush the coating off with a toothbrush. This is a very dusty operation!
Then recoat it again with the paste. You'll probably have to add some more alcohol (or acetone if you insist!) to the old mix to get it up to speed. Glob it on and let it hang once again.
Do this over and over till no more oil is draw.
It can take weeks.,,but it's the only way to completely get all the imbedded oil out.
Ovencleaner (lye) will remove the overcoating of oil and grease from wood and draw oil out of the wood that's down in a 1/16" or so. It simply turns the grease and oil to soap and you rinse it off.
It will not get oil that has seeped into the wrist from the head of the stock.
That deep down oil will weep to the top and spoil a new finish or glue repair. It can reappear in a few minutes to a few days after a treatment.
Using Oxalic acid (wood bleach) is recommended as an after treatment if you do use oven cleaner to both neutralize it and remove the uneven and funky colors that can appear from the process.
Acetone and laquer thinner soaks do not remove all the deep down oil either.
I've tried them all and though some of the methods will remove a great amount of oil and grease from the surface to get you started toward a clean piece of wood,,the whiting powder is the only way I've ever really found to get it completely clear of oil.
It's a very slow process for sure. Have plenty of other work to do in the mean time.