Reshaping an acer

Hi everyone, I took my 15 yo potted acer to my daughter's a couple of weeks ago and planted it in the ground, it's responded really well. Because it was in front of a larger acer it's a bit sparse around the back. I remember a section on gardeners world with Chris Beardshaw where he notched above and below a node? to stimulate or to stop new growth from a branch, i can't remember which is which. Can anyone help?

 

Logically, if you cut the flow of sap just above a node, that stimulates the plant to produce hormones which cause a bud to form and break below the cut. I've got to tackle an elderly Acer p.d. ornatum which is spreading outwards at the expense of the leaves on top. But that's going to have to be amputation, fingers crossed and pray like mad