Posting this because the usual advice is "just use Bulk Create" and it skips the part that breaks.
Spreadsheet, one row per pin: headline, URL, which template, which photo. I write all the headlines in one sitting, completely separately from designing, because flipping between writing and designing is what kills me. Then Bulk Create fills the text, I swap photos by hand because that never automates well, export the folder, schedule.
The bit nobody mentions: every description has to be different. Pasting the same description onto ten pins pointing at one URL is how you quietly get throttled.