To completely convert a nes game into optimized 3D form, firstly we should go through the game and create a series of save-state at key points. That's 30% of work.

- Use Genie Code for walk-through

Save/Load feature is very helpful but for some hard games, it will still take a lot of time to do it. With genie-codes you can greatly speed up the progress.  3DNes for now haven't supported genie code yet but you could use the third-party tool below to inject any genie-code into roms:

Game Genie Guy Tool

- For a game, create a series of save state at graphical key-points  

- After have a overview of the whole game graphic, start editing it.

If you want a game to be remastered but don't have the time or skill needed to do it,  providing a collection of save states is a great contribution for the game remastering process.