How can I achieve a light-painting portrait without the subject becoming translucent?

I know about light-painting. But, when I try portraits with light painting, I get a transparent image of that person in the portrait.

My steps are:

1. Set my DSLR in Manual Mode.
2. Change the Shutter speed to 30″ and balance the exposure.
3. Shoot with FLASH ON (as the flash goes the person stays still for a second and then does the light painting)
4. The final output will be a transparent image of that person with light painting.

How to achieve a perfect portrait with light painting?