1st round of fluid exchange (made simple?)

[Shel155]

02 S8. Please excuse the potentialy blasphemous nature of the post. Ready to do new filter and fluid exchange. Could I not... for first round, when good and cold and the fluid is not expanded, merely drain whatever drains, measure precicely, and replace that? Then a day or so later do it right? Trans is running perfectly right now, but it's pretty brown looking. Thanks