+1 for feet
Didn't read link but assuming it is non bonded like you say and just a weather strip, apply some soapy water around for lubrication, find an easy point to get started, and keep this open with a fashioned wedge of some sort.
Can either push with feet from there, or (and what I would do 1st) if you have some plastic/nylon cord/washing line - ie not too thin - double it over and thread loop through your gap, then pull a bit each way, so that eventually you meet up with yourself halfway around, detaching the weather strip as you go.
Its simple in practice but awkward to explain.