I am very used to using the aztek 470 and spraying using my thumb to depress the spray "lever" when I use the HP-C I want to use my index finger but can't get the right pressure using my finger, the lever is too stiff, is this just a matter of practice? or can I loosen teh tension on the spray lever?

Probably just a matter of practice. But you can get a Rubber safe lubricant and apply it to the little sten below the trigger. I've yet to have this issue with either of my Iwata ABs so I realy don't know anything other than what I already said. HTH STUG