Hi Ponymonroe: Here is a site that addresses this issue:
Or maybe this one from a Hometalker: https://www.hometalk.com/1718866/great-stain-remover-for-carpet-upholstery
Or, mix a cup of vinegar, a few drops of dish soap and about a gallon of hot water in a bucket. Then dab the mixture into the stain and use a brush to scrub it out of the seat, use clean water to rinse the seat off.
Here are a few options for you to look at. https://www.hometalk.com/search/posts?filter=how%20to%20clean%20upholstery
I tent a carpet shampooe and use the upholstery attachments .
I like using Spot Shot.
For my car fabric, I use hot water and dawn dish soap, it works great