Stroboscopic motion photography help

[big_apple_ken]

Just started to dabble in this. A few things I wanted to ask:

1) When I am moving around and the strobe is going off it will yield multiple 'images' of me. How do I make 1 image more 'solid' than the others? I don't want them all to look that 'transparent'.

2) I'm still a little unsure about the stroboscopic function of my 580EX II. It says in the manual on Page 24 "Number of flashes / Firing frequency (Hz) = Shutter speed".

So I set the # of flashes to 30 and the firing frequency to 3hz (@ 1/16) power and using that math I should set my shutter speed to 10". The strange thing is:

A) The strobe goes off 12 times instead of 30
B) It goes off 12 times before the 10 seconds are up so the last 2-3 seconds there is no strobe going off

Can anyone help me out? Thanks!

[big_apple_ken]

Figured it out it was a battery issue for problem #2. Anyone else able to help me with problem #1???

[PhotosGuy]

Do you want to do this in-camera or in PP?
Tried Layer Masks for PP? How to Use Layers: The Basics (http://www.bairarteditions.com/pages/tutorials/photoshop/laybasic.html)

Layer Masks (http://www.lunacore.com/photoshop/tutorials/tut003.htm)

Layer Masks - What the Thumbnails mean (http://www.heathrowe.com/tuts/layerthumbs.asp)

[big_apple_ken]

Trying to do it in-camera. That's why it is tricky. I'm quite familiar with PS and layer usage so I know it is quite easy to do in PP.