It all depends on the type of paint, are there any manufacturer's recommendations regarding use of thinner on the tin?
But before you spend too much time or cash on this, check to make sure that copper paints are still legal in your area.
Copper based bottom paint is being banned by many Environmental Agencies, port authorities, etc, because of concern over the build up of toxic concentrations of copper in sediments.
I am perfectly aware that the majority of Wooden Boat aficionados are sensible folk. However, I need to point out that I am an amateur wooden boat enthusiast simply writing in order to try to help other amateur wooden boat enthusiasts. And while I take every care to ensure that the information in DIY Wood Boat.com is correct, anyone acting on the information on this website does so at their own risk.