Woodworker web sites are an excellent resource for tips on dying, particularly when dying turned wooden bowls and vases. Some of the finishes had dozens of layers of dye with sanding between each. Sand where you want it lighter and always start with the darkest dye when using this technique.
With a simple light to dark fade sponging like goat said works great. Have a clean rag nearby. It's easy to apply more than you need. Depending on the brand of dye a little can go a long way.