You are going to get a lot of different ideas. Most folks underexpose their slide film by 1/2-1 stop anyway. The times I shot Astia I got good skin tones shooting it at it's rated speed and not opening up. I also never spot meter the person. I find my incident meter to be of much more use with slide film unless I want something specific.
Astia is good for skin tones because of it's more natural tones.