I would not use armor all. Hubby has often told me that it will cause the sidewall of tires to crack. Something about drawing out the moisture. I've been with him for 24 yrs, in all that time we've never bought armor-all. I don't know if things have changed, gotten better but it's stuck with me, still haven't bought it. I don't think I would trust it on a leather couch. I would find something specific for leather.
I do agree, the magic erasers work wonder on getting stuff off. Hubby drives himself & his brother to work, the passenger side was filthy. I was able to clean it off without using chemicals. His brother is a body man at the dealership, all kinds of nasty on that seat. <shudder>