HI M8.
I did wash my summer jacket/ pants early this winter before going to rest on the wardrobe till spring ( so out any time soon )
I washed it by hand in the bath,,,, using Nikwax
( Loft Tech Wash )£ 4
and it did a great job.....
clean as new.... let it soak for a while etc,,,,, and used a sponge, soft brush on the stain bits.....
and still waterproof.......
although you can also get
TX.direct Waterproofing £6 for Textile if you think you need.
You should be able to get it on any outdoor store, like Blacks/ Snow&Rock etc
or order from Busters,, H&G ..........or alike