What’s the best waterproofing treatment for shell jackets / trousers wise STWs?
Wash in or spray? Nikwax seems to be most widely available but I’ve used the spray before and it was ok but not great. Thanks

I have had good results with Nikwax Direct TX wash in waterproofer.
Wash clothes first with the tech wash, then fill a bucket / sink with a bit of water and the direct tx as per the instructions (in truth I make it much stronger, just enough water to cover the thing you’re proofing)
Dunk in the jacket, mix about and leave in for a few mins then pull out and shake off excess and leave to dry. The remaining can then be used for another jacket / shorts / whatever.
It will leave you harnds and sink waterproof too so will need to wash down after. I don’t bother rinsing the jacket after like Nikwax says, seems to work well.

mate sells this stuff

Thanks both. I like my sink to be waterproof too so quite happy with that!