How to beat any mission on Authentic Plus

A quick guide for all those out there trying for the authentic or authentic plus achievements. A wonderful way to beat any level. With this method, you can clear out entire areas without being detected.

You need 3 things: a silenced pistol, your rock and a good hiding spot. For the pistol, the Welrod is a good choice since it silences normal bullets, so you don't need to bring suppressed ammo for it.

Start by finding a bush (ideally in the shadows; use prone instead of crouch to further reduce chances of being spotted) or a high ledge with some cover. Next, use your rock and throw it near enemies to attract them to that spot. Wait a few seconds for them to run to the rock, then repeat the process, this time throwing the rock closer to you. Do this until the enemies are a few meters from you. Finally, throw the rock slightly beyond where the enemies are such that their backs or sides will be turned to you.

Next, using your Welrod, pick a target that is at the back of the group. This target should not be visible to any other enemy. When you kill this enemy, the others should not see/hear them die and continue moving/searching the area. You can continue shooting one shot at a time killing the person at the back each time. If you miss, or the target doesn't die, or another enemy notices the target was killed, then throw your rock somewhere nearby to get the enemies to focus there and wait.

Remain hidden / out of sight until the enemies are done "hiding". Once they stand up, repeat the process above by luring them to the killing grounds with rocks.

You can also do this tactic with a noisy weapon if there is a sound mask nearby (ie. generator). Just make sure you kill the target with a single shot and if you miss or the target doesn't die, then stop firing and use your rock to distract them / stop searching for you.

Officers can be annoying so try to eliminate them first. Otherwise they might send soldiers towards your location one at a time, potentially revealing you if you fire on them or they get close enough. They can also cause all soldiers to remain hiding until the officer is killed - not sure if this is a bug or intended.

Examples of where to use this strategy:

Level 1: Practically anywhere since there are a ton of bushes. Ignore the sniper tower at the start and find a bush near the road, then use this technique on the first few soldiers you meet. Try it near the town and you'll be able to clear out both the town and the military camp nearby.

Level 2: From a rooftops in the town. Can be used on people in and around the town.

Level 3: Lots of high ledges around the camps/houses that can easily be used. There is a generator and a few bushes near the bridge where the tank is, allowing you to not only kill nearby enemies, but lure enemies from the bridge with a sniper rifle.

Level 4: Rooftops where the searchlights are. Areas where there are higher ledges that you can hide behind.

Level 5: On the wall in the castle (if you can get there undetected). From the rooftop in the first village. In any of the shaded bushes around the map. On the church rooftop, luring enemies into the church.

Level 6: On the concrete roof next to the first big gun, use the ledge nearby to kill enemies below. On the bunker entrance roof (sandbags). On the walls/ledges where the radar dish is (south side, else snipers will shoot at you). From the upper walkway in the area with the arc generators.

Level 7: Bushes/hedges around the map.

Level 8: High walkways that you can hide on top of and shoot over the side. The 2nd floor of the circular reactor room.

Example of some ideal spots in mission 3:

Example of a spot in mission 6:

Miscellaneous screenshots: