The idea is that if your leather is bone dry it will suck up a ton of dye as fast as it can and that will create blotches and streaking.
How to dye leather evenly. The increased moisture of the leather helps move the dye around more evenly reducing the potential splotches and streaks. To dye white leather black dye it green or blue and then black. Before you begin its best to prep your leather.
As a side note doing multiple passes of water based dyes will eventually dry out your leather. For white into bright red first yellow then red. Unless Im dyeing black I stay away from daubers rags and sponges.
By dampening the leather with oil the dye gets diluted in the moisture and dispersed across the surface of the leather. Use your clean applicator cloth or sponge to apply a thin layer of leather oil to the surface of your couch making sure each nook and cranny is coated. - Use tape to cover any hardware you dont want to dye.
Hydrated leather will better receive the dye. Apply the sponge on the leather sneaker distributing the dye in long even strokes. Oil your leather before using oil based dyes casemoisten your leather before water or spirit based dyes.
Dampen the leather Spray the leather with water or dampen it with a moist sponge until it is uniformly wet. When the dye applicator is first applied to moist leather the leather doesnt absorb a lot of dye. If your having trouble with leather soaking up the dye dont get ANY GLUE ANYWHERE on the leather that you gonna dye and the customer can see if ya do erase it with pencil eraser lightly now if leather stubborn take a 14 cup of simple green cleaner and some warm water and put it in cheap spray bottle shake it up baby spritz leather lightly and evenly.
As it dries flex it occasionally to keep it from becoming stiff. Avoid completely soaking the leather because this can cause it to stain or warp. You can apply one coat for a lighter color or multiple coats for a deeper color.