As my original seal was in a good condition I reused it on the car.
From start to finish I had the seal installed in 20 minutes including installing new anodised gutters and done with no lubrication.
Firstly I installed the new gutters and then pushed on one corner of the seal, seating it on to the protruding part of the gutter that goes into the seal.
I then pushed the downward part of the seal into the gutter so only the inward part of the rubber was correctly seated in the gutter.
After taping up the gutter and paintwork to avoid any scratches I then took a cell phone opening tool and pushed the outer part of the seal in place.




Here's the tool I used. I only used it as I had to it hand and it was less likely to do any damage if I slipped.
https://www.ebay.com/itm/6-piece-Repair-Kit...675.c100623.m-1
Sorry I didn't take more photos of the process. The whole process was over so quickly.

I hope this helps someone out.