What are favored sealants to use before sanding in an oil finish?

Pilkington's method of sanding in an oil finish is the only one I am familiar with, LC, and I don't recall those (lengthy) directions making use of any type sealer, ahead of the process.

Are you thinking of something very thin that would penetrate the wood deeply?

I like Daly's Seafin Ship N Shore sealer.

https://www.dalyswoodfinishes.com/store/index.php?main_page=product_info&products_id=2

I always understood that the secret of a really good oil finish lay in it being in the wood, rather than on the wood.

Therefore, whilst a grain filler may be required, a sealant would seem to be contra-indicated.

LC,

Regardless of whether you choose a product like Pilkington's, or a quality tung oil, or a combination of perhaps tung oil and marine spar varnish......one usually begins with several soaker coats where it's one part of finish to as much as four parts turpentine or paint thinner. That 1:4 mixture will be so thin in nature and penetrate so deeply that you needn't worry about a sealant. Following those several coats with adequate dry time (usually 24 hrs.) you can then begin your sanded-in applications using the same oil at a 1: 2 ratio. Hope that's of some help.......

The traditional sealant for use under a n oil finish is "Garnet Shellac" usually Garnet French Polish Polish with about 25% more Alcohol added. More modern sealers are in the photograph my first choice is the Shellac sanding sealer, with the Cellulose version for no added colour and very rapid drying.

SH-I am following SDH process described in his original Double Gun book. He uses a thin sealer to waterproof the stock before sanding in finish. I have a spray can of Spar/Urethane which seems to soak into raw wood well. I may use it before finishing with Tung Oil or the Birchwood Casey oil finish.

Don't think Pilkington's products are available anymore.
JR

Among luthiers, good old TruOil has been having a real growth, and from experience in both, I believe the expectations are even higher than for gunstocks. It is generally applied as sealer, filler and finish. Heavy coats are used fir saturation, followed by sanded in coats and finally polished coats. A second method that I have tried that gives unbelievably good results is to seal and fill with epoxy followed by a rubbed oil finish. Older epoxies didn't work well for this, but there are new epoxies available just for this service that do.

Pete Hiatt in Oregon has an explanation of his system on his web site. I tried it, and it worked very well. That doesn't mean that other approaches don't work.

His products are not, but one can make the finish that he sold very easily. Supposedly, it is 50% pure tung oil and 50% water soluble spar varnish.

The moment I see the words Tru Oil my blood pressure rises a couple of notches. A lot of money for a small bottle of wiping varnish, it is just the standard 1 : 1 : 1 mix that has been around and used for more than a centaury. On this side of the pond we call it a product health and safety sheet so what ever you call it on your side of the pond obtain one for Birchwood Casey Tru Oil and you will see that it is one part oil one part varnish and one part solvent carrier they always hide the varnish as modified oil meaning they have added a resin.
So lets make the stuff!
Two teaspoons of quality linseed oil. two teaspoons of varnish your choice but NOT!! Polyurethane varnish (Spar varnish was the traditional varnish to use but today hard to find the real thing because they use a synthetic resin rather than Copal plus Tung Oil is far to expensive to use for paint store varnish there are far cheaper alternatives, finally two teaspoons of solvent carrier (turps substitute, mineral spirit, paint thinners). Minimal cost to fill your expensive over hyped Tru Oil bottle.

A far nicer version is one part Tung Oil or one part Edible Linseed Oil (sometimes sold as Flax seed Oil) one part quality varnish (S0 called Spar Varnish has a colouring agent in it to counteract UV so not good) 1 part pure Turpentine (it works well and I like the smell) though you van use what ever substitute for this you like.

Please try to keep in your mind that it is not the finish that produces a good result IT IS THE FINISHER!!