I settled on the Tru Oil/Spar Urethane combo for my first bow. I remember some other guys asking questions about it before and figured I'd post some of my observations. *Note-this was applied to a glass back/belly longbow, not a selfbow.
I sanded the bow all the way down to my fine steel wool and wiped it all down with a washcloth I stole from the drawer. After making sure all particles were removed as best I could, I applied the first coat of Tru Oil using my finger. I tried keeping the oil on just the wood portions (from some of the reading I'd done) and off the fiberglass. I set two dining room chairs a few feet apart and after I thought I had a good coat, I just laid it on the chairs to dry. I put 4 coats total of the oil on the bow and sanded it with the fine steel wool (wiped off before next coat) in between each coat. The oil left a really nice looking, shiny and smooth finish.
One problem encountered-I couldn't manage to keep the fiberglass completely free of the oil. I wasn't sure what it would look like under the urethane if I left the smudges, so I ended up taking some coarser steel wool, getting it off, then sanded again with the fine.
I also read that if I used a sharpie marker to write on my bow, it might bleed or smudge on the Tru Oil. I used a scrap piece of actionwood from the build and put the oil on it as I did on the bow. I used it as a test piece and found the sharpie had no problems at all. I did find that a fine point marker from a craft store that was otherwise "permanent" wiped right off the Tru Oil surface, even after several hours.
I hung the bow in my garage and began applying the urethane. A great guy on here told me to be sure and follow the instructions on the can. It says you need to put your coats on no more than 1.5 hours apart, otherwise you need to wait 72 hours. I put on several coats today and it's drying nicely in my garage. The semi-gloss dulled the oil's shiny finish somewhat, which I'm happy with. It's not the smoothest, nicest finish, but for finger and rattle can application, I can't complain.
For those of you considering trying the combo, I found no significant problems with it at all.
Jeremy