I've never used Scotchgard, but I'm wondering if it would make a wind blocker and wind pants sufficiently water resistant to use as rain gear. This could also double as a light shell over insulating layers when it's not raining. Has anyone ever tried anything like that?

The other idea would be to brush on thinned silicone sealer like people sometimes do with tents. I would think it'd still be cheaper than buying dedicated hiking rain gear.