Using a low cost hand siphoning pump is about the next best way to remove some ATF, versus dropping the pan. But remember that there is a bunch of fluid in the system, a good 12 quarts or more. Siphoning will only remove a small amount, maybe 4-5 quarts, depending on how patient you are to wait a long time and siphon a little more. The pan area of a trans will only let out a few quarts, the torque converter will hold about four and not let it go without a drain plug in it, or half if you drop the valve body. Dropping the VB will allow several more quarts out of the case and TC, fluid which will not come out without dropping the VB. So if the fluid looks perfect you can be okay with just removing a few quarts every so often. But if the fluid seems poor or you want it all out, the pan has to come off and you hope to also find a drain plug in the torque converter.