I also got a wonderful book for Christmas (requested by me!) Eco Colour: Botanical Dyes for Beautiful Textiles by India Flint which is full of information about using nature for dyeing purposes. (I am still working my way through it.).
This is only my first attempt but I will certainly be trying other methods of dyeing for sure. I simply boiled the avocado skins in an old saucepan not used for cooking for about 15 minutes and then added my fabrics -various types of lace, broderie anglais, canvas, an old piece of doily and other trim and then boiled that for about 25 minutes. I am so pleased with the colour - it is such a delicate shade.