The key factors are finding and removing (by brushing and soaking) all algae, and to maintain SLAM level as thorough as possible. That much algae will consume a lot of chlorine. The more often you get out there to test FC and top up with bleach to maintain SLAM level, the faster you will be done with the process. All chlorine above SLAM will get lost very quickly, you'd just run out of bleach very quickly. That vibrant green will take its time to get cleared, but it has been done many times, you'll be OK, just be patient, don't give up.
But at CYA 80 it won't be easy to maintain SLAM level, it will take lots of chlorine. Probably more efficient to do a partial drain/refill to get CYA down.
Once you can see the bottom, you use the pool again with FC up to SLAM level.
And once you're done: Remember that the min FC is a limit you never want to be under, always maintain a safety margin to the min FC. That is your buffer if things go wrong. Ideally you'll always try to stay within the target range.
If you know that you'll have a higher chlorine demand, like when having a pool party, especially with little kids that might leave a no 1 in the pool, than top up before people get in the pool. No harm in getting a bit above the target range, but there can be harm in falling below the min value - not just risk of algae growth, also risk of insufficient sanitation.