Fitz,
I do this all the time (never had help!). Here's how I do it:
1. With canoe upside-down, drill from underneath through the filled canvas at a few spots, including the rib screw locations nearest bow and stern.
2. On the outside, snap or draw a line connecting the holes (the extra holes drilled in center screw locations will help assure you that your line is straight and correct). If you use a chalkline, just tie one end off to a nail inserted through one of the end holes you drilled.
3. Measure out from the line half the width of the keel and mark at a few locations (an indelible pen like a Sharpie is easy on the eyes). This will be the edge line of the keel; one edge is sufficient.
4. Apply bedding compund to the keel, position it along your marks, and then weight it down somehow. I have thought straps might work, but because I worry about the keel moving, I choose more force. You could brace from a ceiling, but because I prefer to work outdoors in the Florida breezes, I place a folded moving blanket on the canoe and over the keel in two places, and add a cement block to hold the keel down- no budging here!
5. Pre-drill if needed, and add screws, being sure to pull the keel down tightly. After applying a few screws in the areas around each weight, move the weight to new areas, checking that keel is still on the mark, and keep adding screws. Adding final attachments from outside through the keel and into stems requires nothing special, of course.
Quick and easy, works like a charm every time, always perfectly straight, no slippage, and no damage to filler or keel.
Hope this helps,
Michael