The invention provides a method for the application of a treatment agent to a substrate, the method comprising the treatment of the pre-wetted substrate in an aqueous system comprising the solid particulate treatment agent in a closed container, the treatment being carried out at a ratio of liquor to substrate which does not exceed 2:1. Typically, the method is applied to the dyeing of textile fibres at liquor ratios of ≤1:1 and is carried out in the absence of additives conventionally included for the sole purpose of promoting dye uptake by controlling electrical interactions or otherwise enhancing interactions between the substrate and the treatment agent. The invention also provides a method for the removal of surplus treatment agents following application of said treatment agents to a substrate, said method comprising not more than three wash-off treatments of said substrate with water following said application. Said wash off process most particularly comprises a two-stage process comprising performing, in order, the steps of: a first wash-off of the treated substrate with water in a closed container at a ratio of water to substrate which does not exceed 5:1; and a second wash-off of the treated substrate with water in a closed container at a ratio of water to substrate which does not exceed 10:1.