The
Wiki has a short-technique section for ideas on how these puzzles are normally solved mark, I have quite the time with them on the included Sudoku game in Brain Age for the DS, excellent control setup for that if I may say.
(using the stylus to draw the numbers, or the mark-ups in the cells works wonderfully)
Was curious Gellyware (even though I'm content with my current Sudoku game on the DS), does your edition allow marking up? (aka, putting little numbers of dots within the cell containers which can be used to keep track of which numbers could be the answer, or which ones cant, etc)
Haven't seen any sign of one in all your posted screenshots. If they aint, I find them pretty key in terms of not wracking your brain 3x as much without them.