That pic is hilarious!

Anyway, it will take a long time. That's how all stealth games are. I'm already 10 hours into MGS 3D, and I'm not even halfway through yet. And yes, I'm playing MGS 3. I'm playing the gameson chronological order to understand the story, even if It won't make sense.

Dress appropriately to the locale, select the time of day appropriate to the mission, equip weapons appropriate to the approach you want to take, scout out possible entry and exit points for objectives, "ive tagged all the enemies so they show up as red markers" isn't proper scouting, you need to scout the area for entry points, places to hide, contingencies and scenarios to react to possible outcomes, properly use air support, properly use weapons, properly take buddys based on the mission at hand, basically just execute the mission with the best possible setup, and properly scout an area.

The dog will help immensely with spotting enemies that you cant.
Horse is good for convoy missions, you can get it to shit on the road and the shit will cause vehicles such as jeeps to spin out, so you dont need to use weapons to stop them.
Quiet is good for missions where you want to either go in guns blazing or need support incase things go south, give her a tranquilizer sniper rifle instead of a dmg based rifle, she will put enemies to sleep if you fuck up and get spotted, but only if she has line of sight to the enemy, make sure shes in place and that you can see her green laser sight.

Crawl like a boss, in the shadows, in the grass, hit triangle to hold your breath, take your dog and have him distract the enemies, if you get noticed but not full on spotted, hit the deck and start moving AWAY from where you were spotted because they will investigate that area and potentially scout around it.

If all else fails, take advantage of the weather conditions, rain and sand storms help with infiltrations immensely.

Oh, and shower every time you go back to home base or the enemies will literally SMELL y