Hey Dale! Thanks for digging the lessons.
I use a Line6 POD XT for all my tutorials, and just dial in the tones from there.
Slash is a bit of a tough one, and I admit I haven't really dug into tweaking for his tone, as I haven't taught any GNR on the site. The best advice I can give to start is to look for a Marshall JCM800 (or 900) model, set the bass and treble to halfway, and the mids to around 65-75% as a starting point. Much of his tone comes from his Alnico Humbucker Pickups on his Les Paul, so if you have a Les Paul you might be able to come a little closer.
Hope this gets you in the ballpark ... let me know how it goes!