Success! At least, good enough for me!
Thanks to Stan for his helpful phone calls.
Traditionally I have used the old block and pencil method for drawing waterlines but Stan mentioned he used the plan to measure the waterline from the gunnels at various points along the length of the hull and place marks on the hull at the measured points. You then apply masking tape to align with marks, using good old Mk 1 eyeball to ensure it is straight. I used 6mm Tamiya tape from bow to short of the stern.
For round the stern and under the overhanging counter, I put a length of the 6mm tape on a bit of melamine and used a steel rule and Stanley knife to half its width to about 3mm - again thanks to Stan for his tip! I then chocked up a spirit level with a laser light to align with the end of the 6mm tape and used that to mark the hull every 2cm or so around the counter. The 3mm tape was the applied using these marks and went around the curves with no creasing. After that it was just a case of fixing wider tape/newspaper to the 6mm/3mm tape and we were good to go.
The paint used was a chance buy spotted on the middle row at our local Aldi. The colour is not quite right for red lead and it is a bit glossy when the can described it as Eggshell but for £1.50, I do not suppose I can complain.
The other point is that this is my first plank on frame model and I clearly should have spent more time preparing the bare hull. I toyed with using automotive filler but eventually dismissed that as being too hard to rub down. Next time, I will use some kind of filler maybe less hard than automotive but better than the polyfilla consistency the Balsa lite which I used before sheathing in fibreglass. Applying fibreglass was also a first and there are some flaws where I will try to do better next time.