The tri coat application requires all the base coats be applied first, then the mid coats are applied after. You don't want to inter mix this order by applying a base coat, then mid coat, then base coat, then mid coat, etc.
 
We recommend the following process:
1. Apply 3-4 light base coats first, waiting 10-15 minutes between coats. 
2. Wait a few hours to dry completely before polishing any excess.
3. Apply 3 mid coats waiting 10-15 minutes between mid coats
4. Wait a few hours to dry completely, and then polish any excess away.
 
See this article for help on how to polish the excess without removing all of the new paint you applied:
 
From this point on, the process is the same as for regular base colors.