How is a hand made drawing protected?
As this is a drawing, practically a unique artistic creation, even if it could be reproduced, the appropriate protection is offered by the copyright and not by the regulations on patents.
According to the rules on copyright, rights over the use of the drawing can be claimed immediately, without any formalities, however it is advisable depositing a copy of the drawing at the SIAE, in order to prove the ownership. Once protected, you could contact agencies or offices to propose your own work and, eventually, grant them exploiting rights for the use of the drawing for advertising purposes or other aims.