It seems to me that hanging and drying and grinding is a pain in the butt. It would be Ok if you're selling the castor too just hang and dry. But if you plan on using it yourself, I would open the castor sac and scrape out the contents. Try to keep any of the red membrane out of the scrapings. Then add some glycerin to make a paste. "Keep it simple stupid" Now I'm not calling anyone stupid just repeating an old saying.

Beav, for future sacs should I just cut & scrape it out when I'm skinning or should I still hang & dry them? For personal use.
And what do I do with the oil sacs? Reading on FHA they say don't send them in for auction as there is no call for them.
Thanks

It’s going to depend what end product your looking to achieve when it comes to your beaver lure. Or if you want a supply set aside to mix into a k9 lure/bait.

For oil sacs you can grind them in with the castor as is, milk oil into a separate jar and then grind and preserve the sacs separately and add into formulations as needed/wanted. Or grind sacs whole separately and preserve.

Beaver are the skunks of the water, endless options.

I would just freeze them whole and when you need them just thaw and scrape.

I never saw any reason to add sac oil to my castor. For one thing it's not a natural thing the beaver doesn't add oil to it's castor. But on it's own at a beaver set it will at times out do castor. Sac oil is a non-aggressive type of smell.
You can freeze the oil for later use or there might be a market for it from some lure maker.

The empty oil sacs left to taint a bit are deadly when used at a canine or cat set.

Thank you both