Carpentry and Woodworking - Finishing Doug fir doors?

I have new 6 panel 8'0 unfinished VG Doug fir doors. They're beautiful, although there are a few lighter places in some of the panels. I was going to start with wood conditioner to make the lighter wood come out more uniform. I wanted to Watco oil, then polyurethane them. If I use the "natural" Watco oil, I feel like the light places won't darken to the same shade as the rest. Should I stain the doors first or use a colored oil? If so, what color stain/oil is best for Doug fir? Also what is the best color wood filler (for nail holes, etc.) for Doug fir?

JBuzz,
I don't have answers to all your questions, but I can tell you that a wood conditioner (like Minwax) is used to seal areas of soft wood and rough-grained areas so that they don't soak up more stain than normal and make dark blotches. It may actually prevent you from evening out the light areas on your doors. If you have some experience in staining, you may be able to give the doors one coat of stain, and then carefully go back through and hit only the light areas with additional stain to get them to even out. I'm not sure what you mean by a "stain-oil", but I have always been able to adjust stain to even out dark and light areas. As for a putty color, you should pick out a color from the selection at the store once you have stained and sealed the doors. You probably know that the colors can be mixed with each other to get tones inbetween what is available.