A method used to form a coating on a substrate surface, comprising: providing a source of heated gas and a nozzle for shaping heated gas into a gas stream column coaxial with the nozzle, the column projecting into a spot on the substrate surface, and providing one or more injectors (19, 21) used to inject feedstock into the gas stream column and used to inject a liquid into the gas stream column; establishing a feedstock profile and determining a portion of the feedstock profile as optimal and the balance of the feedstock profile as suboptimal; determining two volumetric regions (15, 16) within the gas stream column, including one first region wrapped around the axis of the column and a second region surrounding the first region and coaxial with it, the first region projecting into a spot on the substrate surface and the second region projecting into an annular ring on the substrate surface, the annular ring coaxial with the spot and surrounding it; injecting feedstock into the gas stream column and adjusting the injection parameters to control the depth of feedstock penetration into the gas stream column so that the optimal feedstock is entrained within the first region of the stream while the suboptimal feedstock is entrained within the second region of the stream; injecting a liquid into the gas stream column and adjusting the injection parameters to control the depth of liquid penetration into the gas stream column so that the liquid is entrained substantially within the second region of the stream, the liquid reducing the temperature of the suboptimal portion of the feedstock entrained within the second region of the stream, and the temperature reduction being sufficient to reduce or prevent the suboptimal feedstock adherence on the substrate surface, wherein at least some of the suboptimal feedstock impacts the substrate surface and acts as abrasive media and removes weakly-adhered feedstock and grit particles to prevent the weakly-adhered feedstock and grit particles from being entrapped in a coating formed by the optimal feedstock to provide a cleaned substrate surface ahead of the spot on the substrate surface; injecting a liquid into the gas stream column and adjusting the injection parameters to control the depth of liquid penetration into the gas stream column so that the liquid is entrained substantially within the second region of the stream so that the liquid impacts the substrate removing debris on and embedded in the substrate; and forming a coating on the substrate surface by depositing feedstock substantially from within the spot projected on the surface by the first region of the gas stream column, the coating, thus, consisting substantially of feedstock deposited with optimal temperature and velocity conditions. providing a source of heated gas and a nozzle for shaping heated gas into a gas stream column coaxial with the nozzle, the column projecting into a spot on the substrate surface, and providing one or more injectors (19, 21) used to inject feedstock into the gas stream column and used to inject a liquid into the gas stream column; establishing a feedstock profile and determining a portion of the feedstock profile as optimal and the balance of the feedstock profile as suboptimal; determining two volumetric regions (15, 16) within the gas stream column, including one first region wrapped around the axis of the column and a second region surrounding the first region and coaxial with it, the first region projecting into a spot on the substrate surface and the second region projecting into an annular ring on the substrate surface, the annular ring coaxial with the spot and surrounding it; injecting feedstock into the gas stream column and adjusting the injection parameters to control the depth of feedstock penetration into the gas stream column so that the optimal feedstock is entrained within the first region of the stream while the suboptimal feedstock is entrained within the second region of the stream; injecting a liquid into the gas stream column and adjusting the injection parameters to control the depth of liquid penetration into the gas stream column so that the liquid is entrained substantially within the second region of the stream, the liquid reducing the temperature of the suboptimal portion of the feedstock entrained within the second region of the stream, and the temperature reduction being sufficient to reduce or prevent the suboptimal feedstock adherence on the substrate surface, wherein at least some of the suboptimal feedstock impacts the substrate surface and acts as abrasive media and removes weakly-adhered feedstock and grit particles to prevent the weakly-adhered feedstock and grit particles from being entrapped in a coating formed by the optimal feedstock to provide a cleaned substrate surface ahead of the spot on the substrate surface; injecting a liquid into the gas stream column and adjusting the injection parameters to control the depth of liquid penetration into the gas stream column so that the liquid is entrained substantially within the second region of the stream so that the liquid impacts the substrate removing debris on and embedded in the substrate; and forming a coating on the substrate surface by depositing feedstock substantially from within the spot projected on the surface by the first region of the gas stream column, the coating, thus, consisting substantially of feedstock deposited with optimal temperature and velocity conditions.