Do not flush transmissions. It brings back up metal deposits and recirculates them all around the inside of the bell housing again. Not good.

Completely drain the fluid, and refill it with Honda ATF only. As lame as it sounds, Honda's ATF is engineered for their own transmissions, and transmission failure has been linked to using outside products.

For optimum results, you can drain a few quarts, add in some ATF, then drain again a week later and completely refill with new ATF.