Wow, the board appears FINE, and I am sure that as you make few more,you would surely improve.
you could use a soft brush, a spent tooth brush, while the paper removal stage, and rub the areas near holes etc in a circular fashion. Stuck paper pieces on the copper areas should not matter. But, on the process, any extra pressure might remove the carbon as well.
Acetone cleaning at the end to remove the carbon is a good and easy process. you may take care of your hands using some surgical gloves.
the initial scrubbing of copper can be less, in order to not to remove copper too close to bonding level. During that stage also, perhaps acetone helps to remove tarnished copper areas. Finger prints or left over grease or oil, would have carbon lifted, necessitating use of marker pen.