I'll try to explain as simple as i can
THE METH LAB; If you go to the middle of the map there is a safehouse. to the right of that there is a gun shop and to the left is the traintracks ..
The meth lab is around that safehouse.
THE BANK; if you look at the road that you need in order to take to the little like island place follow the high way to the safe house and there will be like a left turn .. on that left turn its on the right... in other words look for the like football looking road and its at one of the points on it