I have not yet made my own since I’ve had good results with affordable options. Generally I’ve used Watco. Kind of pushed one of my buttons here so a bit of what I recall on various oil finish components - in the event you decide to try a diy blend:
Watco was originally based on a tung/linseed blend, but evolved since acquisition by rust-oleum. Its attraction was using solvents to aid in deep penetration and speed curing vs the typical tung or blo finish. Now looks to be linseed and soybean oils and a rosin based component. It does not do well for water protection, I generally use it for indoor furniture. I’ve used Tru-oil, made for gun/rifle wood parts so has some water protection, it does tend to build a gloss finish and is not cheap - based on linseed oil and a proprietary modified oil which could be based on tung or an alkyd. These blends could be DIY since they are not complex - basically 3-4 components. Stoddard solvent is commonly used, it’s basically a more refined mineral spirits, “odorless” paint thinner is close. Some blends use a small bit of naphtha to aid penetration. Fwiw, alkyds are based on polyesters - simply made from fatty acids - if you’ve had a blood test for lipids, you know one, triglycerides - and polyols, which are alcohols. We’ve all heard of methyl, ethyl, isopropyl, well there are a lot more alcohols. Real varnishes, not PU, are alkyd and/or rosin based so make a good base for DIY blends. Tried&True may be a good base. Sherwin-Williams Minwax has an updated varnish based on linseed oil and an alkyd - tough and fast drying. The difficult part of diy’ing is that raw materials, other than boiled linseed oil, tung oil and solvents, are generally limited to commercial products that are already some sort of blend.
Odies and similar incorporate wax - these hard wax oil blends I have not yet used since I’m good with Danish oil. I’m sure the expense of these hard wax oil blends has in part been due to the work figuring out how to get the wax locked in as the oil cures, doubt it’s as simple as adding some wax to an oil blend. Waxes on their own do not form a durable cured finish. In a broad sense, waxes are long chain molecules that do not penetrate deeply so would normally remain near the surface. Simply buffing on a wax after the oil curing leaves the wax in a thin surface layer that will wear off relatively quickly. These hard wax oil blends improved the wax layer to be locked in - the waxes remain near the surface but tightly held in place so less prone to wear. Odies goes a bit further to use all plant based ingredients so cost is higher. But do you need all plant based? Sounds like others suggested some good options.
