And the thread I referenced was done by someone who did it by ear. Lucky there were no broken pistons.
Keep in mind that they guys doing as you cite have a lot more experience, probably better known carb setups, and a 'feel' for this process. Do as you think best but just be aware that you can get carried away. I would gain confidence in the carb setup and not being lean anywhere before tackling timing; lean + too advanced is a great formula for detonation.
As far as timing marks beyond 10 BTDC:
1. Set the engine at TDC. Then move the damper mark CW to 10 BTDC in the timing cover scale, and make a new mark on the damper right by the 0 degree timing cover mark. This is your new 10 BTDC mark.
2. Move that new damper mark CW to line up with the 10 BTDC mark on the timing cover and make another mark on the damper beside the 0 degree on the timing cover scale. This is now your new 20 BTDC.
3. And so on for 30 and 40 degrees if you like.
Now you take your timing from the new damper marks and reference them to the 0 degree mark on the timing cover scale. You can also buy and apply a timing tape to put on the damper that will have fine timing marks on it ready made. Easy to read in fine increments.