Boiled linseed oil is a pretty mediocre finish.
You'd be better off using Tung Oil which is the most water resistant of all oil finishes, and it dries to a better sheen.
You need to get all the old finish off first. Sand with a sanding sponge (work up from 120 to 220 to 320 grit), vacuum off the dust, then buff the wood with some 0000 steel wool. Wipe off all the dust, vacuum the stock, and if you can blow some compressed air on it to get everything out of the open pores in the grain.
Apply several coats of oil with a disposable brush, wiping off the excess with a clean rag. Let the oil dry a day before you reapply, then with a light buffing of 0000 steel wool between coats, repeat the process. About five coats will produce a very nice finish that will repel water and add depth to the grain and figure in the wood.
There is an abbreviated way to do this I am sure, but this comes from my furniture building and finishing experience.