You're also going to need a lawyer with experience with state laws (RCWs) to help you draft the initiative. Some initiatives (even the well funded ones) end up being a pain in the butt to enact or enforce because they contradict existing RCWs or somehow violate the state constitution.

For example, I-502, the initiative that legalized recreational marijuana in 2012. The Legislature had to go in and clean up a lot of stuff before it could actually be implemented, in part because of how it was drafted.