Hello Thibaut,
Your tutorial was right in time and helped me a lot. Thank you. The only one addition is the Source Object must be in the same position as the target when using the Data Transfer Modifier. Took me some time to understand that.
Good call, thanks for pointing that out! Indeed I should have explicitly mentioned it in the tutorial: so the key is to duplicate your initial object before applying any boolean operation and either hide it or move it to another layer. You can also parent the source object to the one you're modifying so that they always keep the same position if you plan to move things around.
/Thibaut.