After finishing my seven year apprenticeship and having worked on some of the big English Estates I got a job as Head Gardener for one of the UK's top Garden Designers Down in west Sussex in a garden open to the public.
He has done gardens in the US and many other countries so he started to train me as if he went away I could supervise the construction of his design for the garden or change things if the client wanted it done that way.
He was a hard task master but I learnt a lot from him for I had done small gardens at the Chelsea Flower Show but nothing as big or as grand as he worked on.
I still today Design for people and always done by hand and then coloured using watercolors, no computers allowed!
Definitely do it on paper to scale with plant lists and the hard landscaping with all the details and specifications on it.
Regards from England.
Neil.