2014 VW Jetta sports wagon TDI

Water is getting in the car. A local upholstery shop removed the ceiling liner and blew out the 4 drain hoses from the roof. Electronics started acting up so I brought it to my mechanic. He pulled the following codes:  P0722; P1793; P1794; 00285; 00668; 03840; 02214; 01316; 01316; 01325. 

5 hours labor to go through inspect for damage water and corrosion.  The ABS switch and an electronic sensor that sends info to the computer were replaced. 

Dielectric grease was applied to electrical connections. 

My next appointment with the upholstery shop is next Tuesday. I'm hoping keeping the car covered will keep additional water out.

I'm going to run a small space heated on the dash from the driver's side floor in hopes to dry out any possible water in the dash. 

Two places I've found water are the driver's side floor; during a heavy rain it was dripping down on my left leg while driving, and about two inches under the spare tire in the back.

I  also find water stains from the ceiling down to the left rear seat. Under the rear seats were wet.

When the car is parked in my drive (front slightly higher then the back) water was draining from the left rear.

You spoke of a device placed inside the car with a sensor you walk around with to find a leak. What is it and is it expensive? Maybe I could get the upholstery shop to buy one or even get one myself and pull the interior.

I guess a through search and drying would involve removing seats, carpet and ceiling liner.  Say it isn't so. 

Please suggest ways to work through these problems.