Yes, you need to pull the trigger to de-cock the gun.
You firmly grasp the hammer, pull the trigger to release the sear, let go of the trigger. Now it is impossible for the gun to fire if the hammer slips. Then you slowly lower the hammer.
How about the Big Bore .375? Thats a brush gun!
Brush busting calibers do not exist. Any bullet, any caliber, any speed, is going to be deflected by brush if it hits it. The best brush guns are the ones that shoot laser flat and with good glass that allows you to shoot through holes in the brush.
For deer size game a very accurate rifle chamered in anything from 243 to 308 is just about the perfect woods/brush hunting gun. Put a quality scope on it to allow you to see tree branches between you and the target and pick the holes to shoot through. Any of those rounds will be no more than 1/2" above, or below your line of sight from around 30 yards out to 130 yards where most all shots will be made.
Rounds such as the 375, 444, 45-70 and even 30-30 will be as much as 6" above, or below your line of sight at the same ranges. The rainbow trajectories even at fairly close ranges make it far more difficult to predict where the bullet will be and greatly increase the chances of it striking brush.
For larger game a 30-06 or 300 magnum provides the same flat trajectory, killing power that has been proven to out perform rounds such as the 45-70. And even the 300 mags do it with about 1/2 the recoil of a hot loaded 45-70 or 450 Marlin.