Years ago i splattered a £90 solid oak internal door (black burn stains)
I sanded the entire side down with a power sander (cheap one) and a detail sander for a few spots, wiped the dust off with white spirit (which doesn't make the grain swell like a damp cloth would) and then rubbed fiddes wood wax into it. it looked the nuts when finished and the customer wanted me to do the rest, which i didn't coz i'm a plasterer not a sodding door stainer
i carry a chamois leather in the van for windows, I sponge them down frame as well and then dry them off with the chamois, fast effective and cheap for upvc.
Like the wd40 tip for the wood window frames though,