Crosslinkable or crosslinked silicone compositions, forming water-repellent and release coating for a flexible heat sensitive support of paper or polymer, and comprising crosslinking polyorganosiloxanes (POSs) bearing ≡Si—H units and unsaturated, preferably ≡Si-Vi, vinyl-containing POSs, capable of reacting with the crosslinker by polyaddition, in the presence of platinum in order to form the crosslinked release coating on the flexible support. The object is enabling the coating composition to crosslink instantaneously to produce, on various flexible supports (paper, e.g. glassine, or polymer, e.g. polyester such as polyethylene terephthalate PET), a crosslinked silicone coating leaving the coating machine, with excellent attachment (adhesion) and mechanical strength or cohesion—“Rub-off”—properties. The invention uses, per 100 parts by weight of silicone base, of 1 to 40 parts by weight of an additive comprising from 1 or 5 to 80% by weight of particulate filler, preferably nanoscale filler, in a silicone oil reacting with the crosslinker.