Mix equal parts shellac, boiled linseed oil, and denatured alcohol. I put the mixture in a squeeze bottle. With the piece spinning on the lathe, squirt the finish on a rag and apply to the work piece. Keep the rag moving until the finish dries and buffs up to a shine.
Quick and simple.
Shellac is a great finish for some items.
Sand to perfection, burnish with shavings or steel wool, then one, or at most two applications of Urethane Oil.
I let it sit for two days, then buff it. Turns out really nice, and it's non-toxic when cured so I've used it on eating utensils and bowls.
This has typically been done when I had a piece of wood that I didn't want ambered from an oil based finish.
A highly figured Maple might be an example where I wanted it to stay white & bright, instead of mellowed. Takes some patience as you have to carefully level your lacquer between coats, etc.
The best it ever gets is a firm & rubbery consistency. I much prefer a Urethane Oil which cures nice & hard.
Apart from it's applicability as a finish, there are some instances where it's the proverbial magic ingredient in trying to get something finished. It's a universal sealer in relation to wacky/oily woods. Specifically, oily tropicals such as Rosewoods, Teak, etc., often keep oil based finishes from curing. Sometimes Pines, especially Pine Stumps which are totally saturated with crystalized Pine resin, often inhibit oil based finishes from curing, or flat out eat the finish away after days, or maybe a few weeks.
However, one to four applications of shellac will seal the nasties away, allowing a finish to then be successfully applied.
One of my turning friends regularly turns really nice stuff out of Pine Stumps. These things SMELL like turpentine, and is essentially hardened resin & wood. The only thing that allows a finish to be applied successfully is several sealer coates of Shellac.
Personally, I feel that varnishes, laquer, shellac, waxes, etc. are not the right choice for pens. Other turnings, fine, but not on writing instruments.
Sand to whatever grit needed to get rid of the scratches; people naturally hold pens closer to the eye than other woodworking projects and they must be scratch free. I would routinely sand to 400, 600, even as high as 1500 grit, the harder the wood, the higher the grit, to get a perfect surface. You may have to start oiling at the lower grits, though, because by 1000 grit you have sanded the pores of the wood closed and the oil won't penetrate well.
Start oiling around 400 or 600 grit (maybe lower), keep the wood wet with oil for at least 5 or 10 minutes or however long it readily soaks in, and if needed, wet sand using oil to the higher grits.
Your surface will look spectacular, the oil has penetrated the wood, and there will never be a surface finish to wear off, bringing to you complaints by the customer. I used to tell people that since they were touching the wood, the wood would eventually take on a patina from being used, and I used that as a selling point, and they loved it. They, and I, enjoyed feeling the wood, and not a plastic surface the other finishes leave. This ain't no Bic!
When it dries, it will look exactly the same as if it had four coats of oil, in a total elapsed time of a half hour -- as opposed to your 5 coats at 3 days between coats, which equals 15 days.