Great answers and all apply. How long it's going to take for the LAB to get done with your mash is dependent on how much sugar there is in there for them to consume. The more sugars, the longer it will take so if you've included any fruit in the mash...
If you want to only give it a week to ferment then as dragonsfire suggested find a really warm place to put it. LAB can handle up into the 90's dF. If the pickle juice your using is from Lacto Fermented Pickles then you'll be helping it with a starter, if it's just pickle juice from a jar of store bought pickles then your probably just adding Vinegar and Water. You'll be better off using some Whey from a tub of Plain Yogurt with an Active Culture.
At the end of the 7 days, check the Ph. If your below 4.0 your golden. If not then use something like Rice Vinegar which has a very mild flavor to lower the Ph. below 4.0 and process it.
Best of luck with it, Cheers