To be frank, defensive Chandelure is a rough idea in doubles due to the common use of Rock Slide spam. But, if you were to build a team that heavily supported around an Assault Vest Chandelure (You mentioned that as the preferred item, so I assume you just want a set with it)
Chandelure @ Assault Vest
Ability: Flash Fire
EVs: 248 HP / 252 SpA / 8 SpD
Modest Nature
- Heat Wave
- Energy Ball
- Shadow Ball
- Hidden Power [Ground]
This is probably the best thing to start building with. High special attack, surprising bulk against special attackers, and Heat Wave can knock a few things out.
In doubles, adding Inferno to Chandelure's moveset and running it with a No Guard (Mega-Pidgeot, Machamp) user is a viable strategy to inflict burns easily while still doing massive damage. Though, if you decided to go that route, I would probably recommend just scarfing it and invest your EV's in speed instead.
Also,
Chandelure @ Air Balloon
Ability: Flash Fire
EVs: 248 HP / 252 SpA / 8 Spe
Modest Nature
- Heat Wave
- Will-O-Wisp
- Pain Split
- Shadow Ball / Hex
Another slightly more defensive variant that can come in on EQ users. But once again, Rock Slide is a bit more popular in doubles than Earthquake and still pretty much screws you.
Choice Scarf + Inferno with a team mate like Machamp (Who I'd stack with protect to further avoid fake out spam) for speedy painful burns is probably the best way to go. I would definitely run double stab and keep Heat Wave in the set as well if you go that route.