I have read a few posts/links regarding additive rendering and I know a lot has changed since version 1.1. but is there a simple and direct way to come up with an image like this? 
I have my particles moving the way I want but I want to play with the additive density so I can control the overall look of the wispyness.
Yes, some things have changed since 1.1, but in general, you should be able to just check >Force Additive Mode and you should be ready to go.
When >Force Additive Mode is checked, the content of the Color channel is copied into the Emission channel internally, while the Color and Absorption are both set to 0,0,0. Obviously, you should make sure your particles have a valid color.
As result, you get fully additive particles. Notice that it is now possible to MIX volumetric and additive shading by tweaking the content of the Color, Emission and Absorptions channels as shown here:
thinkboxsoftware.com/krak-mi … and-volum/
Also, see the bottom of the basic tutorial for the 1.6.x way of rendering additive particles:
thinkboxsoftware.com/krak-ba … rendering/