Select the GO Bank job and this can be completed on any difficulty. Make your way to the back of the bank either through the garage to the right of the bank or the store on the left. When you get to the back you should find yourself in a parking lot. Now equip your mask and climb up the ladder onto the top of the roof. Go over to the sign near the front of the building on the roof that should say "Roberts bank of savings and trust" When looking at the sign aim at the letter T in the word "Roberts" and shoot the letter T twice or however many times needed to make the T fall upside down.
If you want you can do this with a silenced weapon to not alert any civilians or cops nearby.