Blanka725 - Welcome to Autopia. Fellow '02 WRX owner here. After you clay the car, you shouldn't need to rewash unless there's noticeable clay residue. If there is, wash it, otherwise the GEPC IS a good paint cleaner so you'll be OK.
I STRONGLY urge you to use foam instead of terry. Some Subaru paints are sorta soft and the terry will swirl them up. Nah, don't do the direct-glove-application. Foam and microfiber are the way to go.
Maybe consider using something like
Klasse if you're gonna drive the car in the winter. WV's weather isn't much better than Ohio's and P21S isn't always tough enough for winter.