Short answer as already stated...definitely smoke first....and I agree on avoiding the liquid smoke as much as possible...
But I am curious. I assume you are only cooking a flat, and not a full brisket, unless you are planning to do this in a tub. And I also assume you are going more for a slow cooker style brisket, rather than a true BBQ brisket.
If not I don't know how you are going to get that delicious bark without the low and slow process. Either way I think you will wind up with some delicious meat....just to me they are completely different end products. And in my opinion, you can never go wrong sitting for the long haul and waiting...albeit impatiently... for the final product of a true 16 hour full brisket, melt in your mouth, dry rubbed goodness.
That said, if it is a time issue, there are some guys I know that will smoke a brisket at 350 degrees for about 3 hours, wrap and return for about another 2 until it gets to an internal temp of 205 then they take it off the smoker, wrap in a towel and let it rest in a cooler for up to 8 hours. It's still nice and toasty when it is served. In my opinion a little mushy, but so delicious!