Not to get too far off topic -This is called a poor man's flush, and its the second best way.
The best way - IMHO - is a a poor man's flush with a helper - the helper starts the engine - you pour fluid down the dipstick at approximately the rate fluid is coming out into the bucket. The helper is there to stop if you get behind. You keep this up until the fluid coming out runs clear, button it back up, and add / delete fluid until your at the correct level.
However I agree that in most cases a drain and fill is sufficient.
I've always wondered if you don't have a helper, is there any difference doing it this way:
- Run the engine until 2-3 qts. is pumped out.
- Stop the engine.
- Fill new fluid thru the dipstick 2-3 qts.
- Repeat 1-3 until fluid runs "clean".