: Following some internet plans, I roughed out a Greenland paddle and began
: sanding it. Once I finish working through the sanding phase, what should I
: finish it with?

Boiled linseed oil is popular and produces a soft finish. It needs to be reapplied regularly. As Don noted, mixing a bit of varnish with it makes it more durable and waterproof, without making it glossy.

The paddle I'm currently working on will be finished with a blend of 100% tung oil and varnish. According to Bob Flexner's book (Understanding Wood Finishing), tung oil is less waterproof than linseed oil, but the addtion of varnish will compensate for that.

: Should I bother doing something to protect the ends?

On my full length paddles, which get used a lot, I like to reinforce the ends with 'glass or dynel. I leave a narrow flat (1/4" or less) on the edge of the tips, then laminate several layers of fabric and epoxy over it. Once hardened, it's easily shaped with sandpaper and scrapers to a rounded profile. I also coat the last three inches of the blade faces with epoxy for protection. You can use clear epoxy if you prefer, but I usually mix some white pigment into it to give the paddle the "bone tips" look. I've been told that the white tips are very visible when I'm paddling, which is an additional benefit.

For storm paddles, which get carried on deck as spares a lot but rarely get used, I don't bother to reinforce the tips. This prevents them from gouging the deck when I slide them under the retaining cords.