Expert witness experience / questions

Hello - I have a background in relocation services and was just an expert witness for a court case that involved a fall during a move. I was wondering a couple of things:

1. If i wanted to continue to do this, are there any specific certificates I should look into? I was thinking of doing an OSHA training, but was wondering what else is out there. I would be looking into getting more expertise in workplace safety.

2. Is there a way to market my services as an expert witness?

3. What stands out with expert witnesses you've worked with in the past - regardless of specialty?

4. Has anyone ever been an expert witness and would be willing to DM? This whole thing landed in my lap and after being paid I'm definitely thinking I can maybe do this as a side hustle.