An aqueous polyorganosiloxane (POS) emulsion which can easily be deposited on/applied to a fibrous substrate at high speed and at limited deposition rates, for example less than 40 g/m2. The emulsion contains (A) a POS with ≡Si-vinyl units, (B) a POS with ≡SiH units, (C) an adhesion promoter, (D) a catalyst, (E) at least one surfactant, (F) optionally a POS resin with ≡Si-vinyl units, (G) optionally a crosslinking inhibitor, (H) optionally a pH fixing agent, (I) optionally a formulating additive, (J) optionally a filler, and (K) water. Adhesion promoter (C) is selected from protective hydrocolloids, hydroxylated silanes and/or POS carrying at least one hydroxyl group and at least one salified amino group per molecule, and mixtures thereof, and is present in the range from 0.005 to 10% by weight, based on the silicone phase. Also disclosed is the corresponding coating process and the coated substrate.