A process for the airless spray-coating of a surface with a aqueous-containing Newtonian or non-Newtonian architectural coating composition wherein the composition can contain an associative thickener and is subjected to a pressure of from 2 to 5 bar generated such as by a hand-operated or battery operated electrical compressor and then sprayed from a slot-shaped outlet orifice (52) in a nozzle (50) to produce an outflow (31) of composition having boundaries (35) which diverge at least until it has formed a front of at least 30 mm in width. The composition preferably has a Brookfield viscosity of at least 0.5 pa.sec and a solids content of 7 wt %. Also apparatus for performing the process comprising a container containing the coating compositions together with a nozzle having an outlet orifice, a compressor and a pressure release valve actuatable in the pressure range 2 to 5 bar and preferably an auxiliary orifice upstream of the outlet orifice. The process and apparatus enable the viscous compositions to be applied quickly using low pressures easily generated by a hand compressor.