Wow, blackberry juice is hard to remove. For clothes, the best I have found is pouring hot water from the kettle through the stain. It is best to place the garment over a container in the sink when doing this. My Mom used cheesecloth to strain any seed fruits when making jam and jelly.
My Dad had a huge blackberry harvest and my Mom would freeze a lot of them for winter deserts. She would wash them and lay them out on wax paper covered jelly roll pans and freeze them. Once they were frozen solid, she would put them into freezer bags. She made many a cobbler, breads and muffins with them.
Hopefully when you are enjoying your blackberry jelly this winter, you can have a laugh over the incident.