Firstly, colour your image and correct any areas where you have gone outside the lines with your blender 0. Allow the blender to dry thoroughly.
I keep two blender markers - a nice juicy one for correcting mistakes and for blender techniques, and a second dryish blender for softening areas of colour. I find if I use a juicy blender for this I end up with rings on my colouring where the blender has left a puddle on my image. So for colouring an "aura" I usually take my BG10 marker and my BG0000 marker, in addition to my dryish 0 blender.
Taking your BG10, carefully outline your image trying not to touch the coloured image as you don't want ink running into your aura. (Tip- If this does happen, allow the area to dry and then use your BG10 to "push" the darker ink to the back of the image as lighter colours push darker colours away).
Then using your BG0000 and the side of your marker tip, flick outwards from the outline approx 1 - 1.2cm (or 1/2 inch). Don't worry too much if you can see the flick lines. We will fix this up. Go around the entire image doing this. If you find the BG10 line has dried a little and isn't blending with the BG 0000, go around a second time but only flicking 5mm (or 1/4 inch).
Using your dryish blender 0 marker, blend the outside of the flicks so they disappear and you are left with a gradual fade. A close up view:
A little bit furhter away:
Lastly, here is another example using G0000 to outline and flick (the image is a new Whiff of Joy release for November... I'll be posting the finished card later today - I hope, lol).
This also looks really nice with the V and R groups. I hope you find this useful! I would love to see your finished works using this tutorial, so please let me know how you go!