Washing back with large soft mop brush should not disturb the already waxed lines.
Mix a small dollar store pump bottle with one part Ivory Liquid, to two parts water. Pump an amount onto the brush and wash back the color. Wash back over a sink and finally rinse the egg well with cold water. Before continuing with the newest waxing and dye color, examine the egg for any flaws, such as missed waxing or missed color.