Certainly, I'm no expert on this one but you mentioned a few 'places/surfaces' you want to clean. If all the surfaces are flagstone, you needn't find out what the other surfaces are. On the other hand, if it isn't all flagstone, I'm not sure, but it may make matter what the stone is when it comes to cleaning it. (That's for others on the Forum to determine ...)
As for the grout, if it's all mortar, than there isn't more to add. BUT, if it's, say, sand, let us know. For now, my best to ya and hope this helps.