Yetii ... the description is a bit long, but it is pretty easy to execute ... this is how I do it ... and I just use marine epoxy on the tips.
I cobbled this together from a few batches of paddles, so you may spot differences in the actual paddles, but i am mostly trying to explain the "tipping" process i use.
Get the paddle to the final shape and finish sanded to 80 grit.
Figure out how much tip you want on the paddle (how far up the sides) and mark this on the paddle blade edge (both sides) with a pencil.
Take a piece of scrap 3/4" material (or anything close, this is scrap after all), lay the paddle on the scrap so that your hash marks are about 1.5" from the edge, trace the outline and mark the hash marks on the scrap. Cut out the scrap to the right shape, every shop os different, so use whatever is normal for you to get a close fit to the paddle, I cut to the inside of the line and finish with a Rigid Oscilating sander to the line, then fit close to the paddle.
This pic is further along, but if you look close, you can see the hash marks on the paddle and the dam .... these are for alignment, you will need them. Also notice how the scrap piece (dam) extends further than the where the tip is cut.
The next part is always nerve wracking for me, I use a marking gauge or compass to scribe/mark a 3/8" line (from the paddle edge), from hash mark to hash mark ... I round the line out to the edge so it tapers nicely to the hash mark, then I use the Oscilating sander to sand out the material.
Position the epoxy dam and align it with the hash marks to make sure it all fits snug. I use packing tape to cover the exposed surface on the dam, so the epoxy will release, run the tape across the bottom, sticky side toward the paddle, it forms a sticky blanket when the paddle is put in position. Again, this pic is ahead of where this description is, but you should get the idea.
Position the dam on your work surface, carefully slide in the paddle and try to work the bottom a little to get the sticky tape to stick the paddle close to the edge as is doable (don't overwork, just try a little), clamp the dam and paddle into the correct position using the hash marks.
Mix up your epoxy, use a small brush to saturate the paddle tip (there is now a 3/8" gap between the dam and the paddle), it will take several applications, it is usually end grain and it will drink a lot, i would suggest 5 minutes as a target to saturation. I use wood flour/dust and cabosil (fumed silica) to thicken (think a little less than peanutbutter) the epoxy to whatever colour I have selected ... you can also use pigments in the epoxy. Cabosil sounds fancy if you haven't used it before, bit is pretty standard stuff for epoxy work, it lightens the colour, and makes it less transparent, giving a little more control on final shade. Laddle the epoxy into the tip space between the paddle and the dam ... don't be stingy, overfill by about 1/8" ... it will settle, and it is easier to file off excess than refill a low spot. You want it to look like this ... at least i want it to look like this, so there is lots of epoxy to work with. Check after about 20 minutes and fix anything thats dropped or pop bubbles that may have formed .... you are done till the next day.
Use a rasp file to take off excess epoxy and contour the edge shape, use the sander to do a final rounding of the bottom, sand out to 120 grit and you should have this
And that is how i put the epoxy tips on.
Brian