I'm sure I've seen mention of this technique in the archives, but can't find
it now.
Idea being with my very uneven gaps on softwood casement openers, to:

1/ Open window
2/ Cover opener contact points in suitable release agent (Cling film,
silcone or PTFE spray?)
3/ Seal on to frame in the proper position of a typical draught excluder
with low mod silicone.
4/ Close window to vent position
5/ Time passes...
6/ Open and trim with knife as necessary.
7/ Have lower bills and more comfort.

Anyone like to add anything to help task satisfaction, esp concerning
release agent.

--
Mike W