[Closed] Fabsil on cotton/polyester trousers ?

As in can you use it on them.
Pair of everyday of craghopper cargo type trousers i usually wear on the bike too, but even the occasional splash of rain they get wet through as they arent specifically water resistant.
I've used nikwax in the past to mixed results but im out of that, but do have a fair bit of fabsil from the last tent i did. Was wondering if you can use it on clothing too.
Normally with cotton flysheets its been a thing where when raining you shouldn't allow the outer and inner to touch as it can allow wateer to come through(I've no actual experience of this apart from being told/rumour.
Given trousers are mostly in contact with the legs, would the same type of thing apply, or would it not and just bead on the surface, only a problem is thoroughly soaked