How much extra time does the stern and bow add to the build?

About two months. I built two bows and 1.5 sterns. With the first bow I was unhappy with the alignment when viewed from the side after I had put on few strips and ended up taking off 3 strips and building a new bow. Stern: I built half a stern and did not like the shape. I reviewed viewed Robs video and Etienne Mullers Pole Dancer photos and narrative and decided to build the stern panels in two 3/32 layers rather than one 3/16 layer which tamed the strips considerably. I was also finishing up a canoe at the same time and was ping-ponging back and forth. The bow and stern are built on their own set of forms and do not take up much room in the shop, so it worked out well logistically.

Bits of the paper towel do not stick in the epoxy when blotting?

Not at all. I was using the expensive blue "Steel Tuff" towels for the last three boats I have built, but ran out halfway through this project. I ended up using white cheap and nastys for the deck. The technique: 1) lay out the glass. 2) pour the epoxy onto the sides of the hull(deck). 3) roll it out into a somewhat even layer. 4) tear off individual sheets and place them into the bottom of the hull and whereever you think the epoxy may be to thick or floating the fiberglass. 5) Roll over the towels with your epoxy soaked roller. 6) Peal off the epoxy soaked towels and examine the glass for areas where you might need another towel. This tends to be in the sharp angles near the bow and stern.

IMHO: 1) this is much faster than trying to evenly squeegee out the excess epoxy. 2) My hands do not cramp up, as I am not spending time grasping tightly to a squeegee, a roller handle is a more ergonomic shape for me 3) It presses the glass into the wood so there are fewer (no) spots of bubbles. 4.) No bits of paper towel are evident. 5) No "fiberglass fuzz" is created. 6) It is easier for me to get an even layer of epoxy than with a squeegee. 7) The idea is not mine, I first heard of it here on Kayak Forum as a report from the Bear Mountain Boat website.

I do need to build one of robs designs one day, and pull it out when I need a straight tracker and lots of space.

If you are getting accustomed to the Parking Lot Syndrome (PLS) generated by a Greenland style stripper, just wait 'til you hear the crowd reaction to the Baidarka!