Pro's
1. easy to do and not too labour intensive
2. By using your fingers you can feel whether the glue is being removed.
3. No rags required and clean up is using a vac. The glue isn't sticky
4. no sticky rags and hands
5. no playfield damage
6. Fairly quick process
7. The flour highlights the glue so you can see any missed spots right down to the finest details/specs

Con's
I couldn't find anything obvious