K. A lot of this is someone else's method but I cannot remember the original theorist:
1) Split the board up into 4 quarters
2) We have four pattens, in the bottom left quarter, the patterns are this:
Left diamond - A4, B2, C3, D1
Right diamond - A1, B3, C2, D4
Left square - A2, B4, C1, D3
Right square - A3, B1, C4, D2
Identify which of these patterns the start and end squares lie in.
3) If they lie in opposite shapes (square/diamond) then you complete all the squares that are within the same shape as your starting square. I.E. if you started on C3 and you're wanting to end on G8, the first thing you would do is colour the following squares:
C3, D1, B2, A4, B6, A8, C7, D5, F6, E8, G7, H5, G3, H1, F2, E4....
4) Next, you fill in all the squares that lie within the opposite shape (square/diamond) that isn't the same as your ending squares shape. And then you repeat this stage, and then once more, and you've done it.
5) If the starting square and ending square are the same shape but differing directions, then you complete stage 3 as normal, but when you get to your third shape, you will have to go to that of your ending square, and so you want to complete that shape for everything but the ending square, then go to the last shape you haven't completed, and finish.
6) If the starting and ending square are the same shape and same direction then you basically do step five, but isolate the ending square quicker.
As for doing this blindfold... well, just practice your visualisation really.