We use a machine here, however many newer transmissions (including these 8sp Aisins) have a thermostat in the ATF preheater (the little "box" on the top of the unit with coolant pipes going to and from) that will not allow ATF flow through the cooler until the ATF is good and hot.... which sitting still they often never achieve.
I would just drain and fill it from the drain/fill hole in the pan. You'll only get about 4 liters doing it that way, which is why if it looks really dark you can do it a couple times within a hundred miles or so. Total fill is closer to 11 liters, FYI.
You needn't mess with the filter, it won't have anything in it.
Find a source for Idemitsu TLS fluid, no sense in spending some obscene amount of money for VW-branded ATF for your T'reg's Toyota transmission. They just repackage it. You can often find a 5q bottle on Amazon for about $30. 5 L of the VW branded stuff I just found on eBay for $110.
We've been using Idemitsu fluids in every Aisin box that comes through our doors for decades, never had any issues. This includes [obviously] all the Toyota products, as well as all the Volvos, Jeeps, GM, Ford, Mitsubishi, Nissan, ChryCo, Mini, etc. that use them.
