there is several types of solvers out there. depends on what you want it to do...
compare solutions paths (get many)
they all different by what order they are programed in.. and what is programed in them..
simply a pm filler pic your fill most or all accomplish that.
"frowned apon" never- its your own choice.
techniques do not assume penicmarks are there.
the grid tells you directly without them what can or cannt be in a space.
a technique is the application of combinations of restraints of what could be using only the knowledge given. you do not need pm to find them.
but to show what you mean it usually helps to list them out..
simple sudoku.
http://angusj.com/sudoku/Sudocue :
http://www.sudocue.net/sudoku explainer:
(mentioned above) getting old works well though missing some newer stuff.
hudoku:
http://hodoku.sourceforge.net/{latest and being updated alot
keep up the good work hobiwan!! }
( im liking hobiwans newest one very user friendly you can change the order of techniques or find alternative paths!)