Dealing with foliate detail is tricky, half the struggle is deciding on a system of depiction. Fortunately others have been here before us and following a template makes the job easier. The mason who cut the stone would have been following a guide of some sort so finding the template is half the struggle.
From A History of Architecture on the Comparative Method Sir Banister Fletcher 13th ed 1946:
Using Banister Fletcher as a guide it is possible to find a close match to the vine and leaf on this monument and thus extract the foliate detail as edge lines from the orthophoto:
These are stylised forms based on nature and cut in stone, the drawing needs to show the form as bound by edge lines.
The Internet Archive online version of Banister Fletcher’s encyclopedia is a good resolution scan of a 1905 edition, the earlier edition has less line work illustration than the later editions. It is provided by the Robarts Library of the University of Toronto, it is downloadable as a PDF and can be resized up to 400%before the artwork degrades.
A sample from the 1905 edition on the Internet Archive, some pages are skewed more than others:
Knowing where to find the templates is key to getting foliate detail drawn up.