How Should I Bustle a Side Sweep Train on a Mermaid Wedding Gown?

I would recommend a ball gown bustling as it will be easier to manage where you will pin it up.

Suggestion:

Talk to the alterations people where you got the gown. Mermaid gowns would be hard to bustle because they are tight to about the knees and then flare out. Get some ideas from the alterations people.