Rewriting little by little just means: each time you make a change, leave the source base at least a little better than you found it. Leave a few comments about

Rewriting little by little just means: each time you make a change, leave the source base at least a little better than you found it. Leave a few comments about the thing you reverse engineered. Delete a little dead code. Eventually you get the confidence to move from the lowest hanging fruit to deeper refactoring. You do it because that approach may be the best you can do with a rotten source base within your time and resource constraints,