It starts here:
INPO 11-003 (nee 09-004), Procedure Use and Adherence
NEI AP-907-001, Procedure Process
NEI AP-907-005, Procedure Writer’s Manual
There a few consultants that offer a procedure writers certification, these are no guaranteed ticket to a job.
My experience cannot be comprehensive as there are a lot of places I have not worked. Full time "Procedure Writer" (defined as 40hrs/week, 52 weeks/year, full benefits package, single focus career) is something I have not witnessed for so long I'm not sure they ever existed.
Procedure writers are hired with some regularity for staff augmentation, you may have to be willing to work cheap for awhile because you will be competing against many of the semi-retireds who have deep and proven resumes and established networks.
You could always go NLO, QA, mechanic, etc., and volunteer for collateral work writing procedures, prove you have an aptitude for it, and essentially become the default "go to" guy for that objective. Later, you parley that aptitude and proven ability into a career move.
That last is my best thought as it does not seem from your post you are looking to travel.