So Richard, I've been in your shoes precisely and I understand what the pool guy is trying to do. And what you're going through
I actually did the equivalent upon finding TFP a few years back with a blackwater foreclosure swamp after watching the first $750 effort of a pool guy fail. Your guy is right about some things and wrong about others. I'll try to explain. I'll also suggest an easier option
First off, a pool guy can't possibly hit a swamp hard enough with a
SLAM Process because you need to be testing and adding every few hours over days. So you need to take that over. And to do so, you need one of the recommended TEST kits at
TFTestkits.net.
Once you get a kit and post reliable full set of readings, you may need to make a few adjustments for ideal slam conditions, such as lowering ph if its above 7.2, and confirming that you're holding FC at all...hopefully since you've had color change, you've nailed the ammonia I suspect you opened with.
So, tell pool guy you'll have him back later once you get things sorted, though you may or may not wish to have him do the final bit...depends on how DIY you feel and how much time you have. I had mine back for final vac and equipment check.
As for the organics, if like me you scooped and hauled 20 wheelbarrows or so and can't "feel" any more major obstacles on the floor,
mostly close the bottom drain line and filter from the skimmer while slamming hard, but dont otherwise disturb the water by brushing or vacuuming for a few days.
In my case, i WAS able to see bottom after doing this as you will see in my pic, despite there still being a pile of sludge...but I was working COLD in April. You're working in summer.
If you prep yourself for the slam to go this route, i will check in and will want you to post progress pics and summaries of FC readings to gauge whether you can get there. You'll be looking at a possible few more weeks of commitment to get to the final stretch.
The other route is trash pump with sheet method if your water table is high or unknown. You want the big ones you rent from Home Depot for about $60 a day. You need the hp to get stuff off the deep end. This is a rent-don't-buy scenario, IMHO..
In this scenario, you are pumping off at least the bottom half of the water (pumping sludge, NOT vacuuming sludge...I make the distinction because there seems to be a bit of confusion on this...) and the grinder style pump is sucking up all the debris with it. Objects you've lost, like leaf rakes, may be a problem, so this is not necessarily a panacea. But its speedier. You would add a large tarp or visqueen to separate the water you're pumping from the fresh water you're refilling with, thereby keeping the water level high enough to avoid floating the liner or causing structural shifts in the walls.
If you decide to go this route, I will put you in touch with a poster whose done this for tips if I can raise him

You can tape together visqueen with duct tape, or buy a giant waterproof tarp.
In my situation, I would have slammed regardless because I wanted to knock down the odor and protect anyone working on the pool from contracting any illness. While it might seem wasteful, the proof was in my pool that you can hold and maintain slam level FC with debris in the pool, and you CAN clear it this way.
I have an early morning meeting and a long day followed by an event, but will be happy to pop in tomorrow am early if you have questions about my experience in hindsight and want to discuss which way to go. Just know its doable
Cheers to clear!
PS ...Re pool terms, please start with
ABCs of Pool Water Chemistry - these are terms you'll need going forward anyway

and please work your way through pool school and make sure you're comfortable with your valves, pump and filter before we get rolling
