I've always used TFR on wheel arches and sills, bottom of bumpers and around the wheels but i very rarely use it on body panels if I can help it, You'll soon know if youve mixed too much, if it dries on a hot panel you will quite literally see heat vapours coming off that look like faint wisps of smoke/steam, thats the best way i can describe it anyway

Its a good product to use, but needs to be very diluted.