More effective fire extinguisher liquid than water
You could consider an aqueous film forming foam (AFFF) system, this is water with some additives to form a foam. Originally foam was something intended for class B fires, but there are now foams which are intended for both class A and class B fires. They are even considered to be acceptable for use on gas fueled fires where there is no risk of explosion (class C). Thus there are ABC foams.

A word of warning some ABC foams such as those based on PFOS are horrible and harmful. It might be best if you stick to a water spray system. The PFOS foams are considered to be problem when they enter the environment, if I recall correctly they are very harmful to fish and the perfluoro compound PFOS only breaks down very slowly in the environment.