Ok this in more of a this is how I have done it for years but never had means to ask, or did ask and have forgotten what the reply was.....
when reassembling the seals the outer dust seals have two lips that "brush" against the piston. do you fill the gap with grease or do you clear the gap out. that is to say do you make a conscious decision to make sure one way or the other.
I just smother them with brake grease and wipe up after installing the pistons.