Some garages and dealerships use a machine that attaches to the oil cooler lines of the transmission. Filtered fluid is flushed through the transmission to ensure all the fluid is removed from the transmission. There are pros and cons to "flushing" the transmission. Using a flushing machine can dislodge debris in the valve body and can end up causing the transmission to fail. Your transmission is simple to service there is no transmission pan to remove. A simple drain and refill every 30,000 miles using Honda ATF- Z1 should allow your transmission to operate for many miles to come.