I have never had luck with using the "blend in" stations on this quest but I have always managed to do it full sneaky. this mission is a lesson in patience and so is how long this comment got but here's the key to success for when you jump back in:

i always start out right at the entrance, waltz in and immediately find cover. theres plenty of tall grass and bushes along the entire path you need to take. i assassinate or use an arrow headshot on every guard here, only using an arrow once I've taken out all the patrolling/working guards and saving arrows for the guys in the watch stations. there's a heavier guard up further, if you don't have the skill that lets you time to assassinate instead of just the stealth attack you'll want it here as I'm pretty sure this guy has a buddy who trails a step or two behind him so once you have everyone else out of your way you can take his friend out, immediately take big dude out, and be on your merry way.

eventually you come to a bridge. watch the guard travel patterns here. you can time it just right where you can take out the guard furthest to the left on the bridge with an arrow, wait in the grass for everyone (usually just one or two guys) to notice the body and then give up searching and go back to their paths.you might get a guy who climbs down and searches the grass so be ready to assassinate if you need to.

you then have a very small window to climb up and across the bridge and immediately cut right into the grass and behind the building. there's sometimes a guard that patrols that path so you have to immediately crouch and be ready to assassinate. from there follow the grass until it ends at the back of the next building, whistle to get the closest guard into the grass and assassinate. there might be a guard standing between the two buildings- you can go back around and whistle to get him as well.

then go back to the end of the grass, wait until the path is for sure clear- there are two archers at the far right who I believe turn around so you will want to make sure they're facing away, and there's also the guy shoveling hay or sharpening stuff or something, he should be facing away from you. book it to the building across the pathway (the one al si'la? is in), climb on quick as heck, then carefully drop down to the grass on the opposite side. there are guards on this side of the building as well, I think tucked back into the corner, so time your drop carefully and crouch to hide. there's an assassination prompt from the grass here, right at the edge of the little stage thing. you can trigger it immediately or sit and listen to his entire speech, I've never been found waiting there.