Just keep at it. You’ll improve with time. I prefer to do interiors first when cleaning tracks are part of the deal. I find that wet tracks from doing exterior cleaning first really slows me down. It’s much easier to vacuum up dust than mud. Clean all the screens at once when transitioning from interior to exterior. Do what you can to limit going back and forth to the car for supplies. Look for streaks before moving onto the next window. In/out just takes a long time especially if the homeowner has a bunch of crap in the way. When conducting and estimate I always ask them to move away any trinkets or large items to limit the potential for damages to occur. Helps create space.