How to kill Dozers effectively?

First rule of bulldozers: try not to take one on alone. It's hard to kill a dozer alone. Second rule of bulldozers: aim for the face. That's a Bulldozer's only weak point. But even that isn't very weak. You're going to want something with high damage, and a lot of focus fire to take a Bulldozer down. With enough fire at the facemask, it will eventually break, and expose a bulldozer's face for a couple final bullets.

Assault rifles are quite effective against bulldozers, since they are versatile and still effective at long range. Whatever works for you in that department, really. The AK-762 deals quite a lot of damage per bullet, and has manageable recoil. The AK-5 can be modified to have superb recoil, making the "aim for the face" part a little easier. Whatever you're comfortable with, really. (you can even use the M308, if that's your thing).

Shotguns also tend to be very good against bulldozers (though the Locomotive has a much shorter effective range), but it will still take a lot to take a bulldozer down. If shotguns are your thing, the Mosoni 12G is a superb weapon for the job, since it has such high damage output, and a decent effective range. One of its major downsides is its low ammo capacity at 26. If ammo is a concern, I would go with an assault rifle. The Reinfeld 880 is a good alternative in the shotgun department, since it still has high damage, and still a decent effective range, while carrying more rounds.

In a pinch, the Deagle and the Bronco .44 can deal significant damage to a bulldozer, however, if you have another option, I recommend using that instead. These should be saved for if you're caught without any primary ammo. The white streak, baby deagle, deagle, and peacemaker .45 can all take down a dozer in 4 hits to the face, if you're accurate.

The OVE9000 Saw is by far the fastest at taking down a bulldozer. However, it has some severe disadvantages, because it requires that you run at a bulldozer. So it is not the most effective weapon for the job by far, but if you're carrying the saw, and there's a bulldozer in your face, it takes about 2 seconds to slice right through a bulldozer's armor.

And on the point of trip mines: trip mines are effective at taking out any enemy within the blast radius. Ironically enough, since bulldozers wear bomb suits. I do not recommend trying to set up a trip mine really quickly in the walking path of a bulldozer. I have done it before, and it can work in a pinch if you can set it up fast and get behind something, but it is not something I would rely upon.

What I recommend (depending on the job, but the one that comes immediately to mind is Overpass Escape) is to set up several trip mines around in the general "cops will come through here" path. Odds are, you'll take out a special unit.

With the sniper dlc recentley added (month or 2 ago) the thanatos .50 cal is a dozer slayer 2 head shots (3 or 4 for a skulldozer since they have 10k hp) will definatly kill them. The .50 cal seems to have been added for this purpose though i recomend using your secondary as your main because the .50 cal only has 20 rounds and rare ammo.