This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
The proper time to bud Vines on the dovetail system is in spring, after the Vines have broken into leaf, and there is no chance of the Vines bleeding. Keep the grafts or young growths from which the buds are to be taken in some cool shady place laid in some soil, so that they may remain dormant till the stock is in leaf. The best union, however, in the case of Vines, is formed when both stock and scion are growing, and by uniting green wood to green.
The cause of your Cauliflowers going wrong as you describe, is the very great amount of wet you have, in common with many others, experienced the last ten weeks.