The torque converter doesn't drain, so when you drain/fill you only get about 1/3 of the fluid. If it's real dirty, you may need to do 4 or 5 or more drain/fill cycles. Drive around to mix fluid inbetween. There's no filter or screen that you can change (unless you dismantle the tranny).
Still, no guarantees. There must be a reason why Honda says NOT to 'flush' their automatic trannys. I think partly it's because the flushing machine uses some kind of solvent - not pure ATF.