Hi
Sorry for long delay in posting reply.
A booklet of memorial inscriptions for the Wigtown Old Kirkyard (also known as St Machutus or Wigtown Parish Church) lists a James Johnston died 14 August 1882. The inscription says he erected the stone in memory of several children, and then he himself is inscribed on it. No mention of his wife though.
This is from a booklet published by Dumfries & Galloway Family History Society. The Wigtownshire cemeteries are 26 booklets. Each one contains an index by surname, but unfortunately there's no master index across all books, or by first name (as yet). You have to buy the pdf booklet for the cemeteries of interest.
https://dgfhs.org.uk/product-category/memorial-inscriptions/wigtownshire/(Message me for more info…)
DGFHS are also doing a project to take photos of every headstone.
Yes FindaGrave is always worth a look, and other similar sites like billiongraves
Also the paid subscription sites if you have access to them (eg through a library...). Ancestry has burial records for some cemeteries/some dates in a collection called "England & Scotland, Select Cemetery Registers, 1800-2022". It includes some from Dumfries & Galloway. (Note some Kirkcudbright registers are incorrectly under Kincardineshire). Can be best to browse a county rather than just search by name, to see what cemeteries and types of records are covered).
https://www.ancestry.co.uk/search/collections/9041/DGFHS is affiiliated with FindMyPast, and progressively making information available to them - memorial inscriptions and old parochial records.
You probably know of course that in those days name spellings varied, they weren't considered fixed like today. When people spoke their names, the clerks might record what they thought they heard, spelt as they thought fit.
I visited Wigtown in 2022 (I live in New Zealand). I found family graves and developed a real connection to the place. Finding a specific grave in a cemetery can be tricky. Some memorial inscription booklets have maps, some don't. The Wigtown library has a plan of the graves in the Old Kirkyard, attached to one of the memorials books in their heritage section. I also discovered 2 keen family historians in Wigtown who love to help visitors or enquirers from elsewhere.