I'll add another vote against filler stains. They just muddy up what would be beautiful wood, taking what would have been clear, beautiful wood grain and making it look like what it is - wood with some kind of blah-looking goo spread over it. Some people may like the look and that's okay; just not me. As others have said, this is especially true for the gorgeous mahogany used on these early Old Towns. Cleaned up and varnished, that's some stunning ly beautiful wood! Even with your sanding, I'll be those rails will really pop when you varnish. If you haven't already, give them a wipe with mineral spirits to get just a hint of what's to come come with varnish. I do sometimes use stains - but not filler stains - and dyes and other chemical treatments to match colors, but I use them sparingly and judiciously.
I also agree with Dave (dtdcanoes) that you'll probably be MUCH happier with a stripped and re-varnished interior. Patina (at least by my definition when restoring wooden canoes) is in the wood, not the old finish. Crusty, age-blackened varnish is just hides the beauty of the aged wood. I have canoes that I leave alone because they are so rare, but if this one were mine I would give it a total refinish. Attached here is a photo showing a freshly cleaned-up hull (a 1916 AA-grade Otca) looking way too bright, but after addition of just the first thinned varnish coat it shows the stunning beautiful richness of that aged white and red cedar. I wish it also showed the transformation of the mahogany - the varnished rails were deep and rich in color, contrasting spectacularly with the cedar colors. This photo was in a previous thread on stripping old finishes:
By the way, the canoe below was stripped, cleaned with TSP, then treated with a high-quality 2-part teak cleaner/bleach (Te-Ka or Snappy Track-Nu; the stuff often found on the shelves of big box stores and some marine stores don't work nearly as well... I know from experience). Note that these "cleaner/bleach" solutions do not contain household bleach (sodium hypochlorite). I once saw an 80-100-year-old canoe treated with household bleach, one that should have had beautiful patina and nice contrast between wood species, but it was all a washed-out blonde. It seemed sadly unfortunate.