I accidentally found this trick to avoid completely police attention when you are forced to use a sawn off shotgun to push an indestructible vehicle to a garage. I am sorry if I am going to tell already found one. But still this might be useful who don't know this. No doubt because sawn off shotgun has a high noise, police will always going with ur tail if you ignore whether police is nearby. Remember with duel wielded sawn off shotgun, there is a high reloading time. The trick is to use this reloading time to search police nearby.
Method: Before you shoot to the wreckage with sawn off shotgun, look in front. If you don't see any police cars, bikes or cops on foot, then hold the look behind key to look backwards. Then you can see whether there are cops on behind. If still no police, then feel free to shoot. If you have the sight of wreckage in front of you, using look backwards key doesn't cause to vanish it how untrustworthy it would be. So after you shoot the wreckage and push some distance, sawn off shotgun will take some time to reload. So you have to wait some seconds before you shoot again. So once again look backwards (hold the key and don't rotate the camera) to see whether there are cops nearby. And then release backwards key button to come the sight once again forward. At this time, Sawn off shotgun should have finished its reloading. If you see no cops in front as well, feel free to shoot again. If you see a cop car, bike or a cop on foot, then wait till he is passing you. Before shooting, make sure there are anymore cops in front and behind. Then continue this method until wreckage is very close to the garage. At this point, you may not need to use look behind key for searching police because we have a very few distance to push.
This method is greatly valuable for Allproof Bravura, FCR 900, White Newsvan and Greenwood. When you push allproof Greenwood, this method will not be ease the pressure because of rioters. But still may be useful to remove police attention somewhat amount.
With this method, I could be able to push Allproof FCR 900 without any wanted level upto very next to the Doherty Garage. So I like to give only 3 star difficulty for FCR 900 and White Newsvan.