I didnt watch that video because I have my ways but heres a written reamending guide.
Before the guide.. Something I do is keep all the plant scraps, fan leaves, stems even the roots and cut it all down to 1-2 inch pieces and mix it with some well rinsed coco shells for mulch. But mulching is another story.. I dont put the roots back into the soil like the guide says you can.
Here is the source to the guide that this is copy and pasted from
https://forum.grasscity.com/threads/easy-organic-soil-mix-for-beginners.1116550/ it includes a recipe and the reamending guide, the recipe will not be the same as subcools but just pay attention to the ratios and you should be able to figure it out.. if not please ask and I can help with ratios if you tell me everything in your recipe
Guide....
(( Organic soil can be re-used over and over again. In fact, the soil actually gets better as it ages! Organic amendments take a long time to break down-definitely longer than a single grow cycle and years in some cases. You can even re-use the soil without adding any extra amendments. A plant only uses a small amount of the nutrition available in an organic soil, so remember that there's still a lot of good stuff in there. Soil can be used for several grow cycles without any additional amendments-you can grow for years without re-amending it. Also, if your garden is no-till, then you wouldn't follow this re-amending procedure. Just top-dress with some extra "goodies" every so often.
It's important to note that re-amending your organic soil is an art, not a science. While the recommendations I've made below are good, your soil may need something a little different. If your plant showed any kind of deficiencies, you'll need to amend the soil to correct for those now. Ultimately you should trust your gut and go with what you think is best over following a prescribed formula. The only thing you should absolutely add more of is your humus, and then any extra aeration amendment needed to offset the additional humus.
I like to lightly re-amend after each grow cycle or two to keep a steady supply of amendments in multiple stages of decomposition. After harvesting, pull out the root balls and soil and dump them in a large container. Use a shovel to chop up the roots as best you can (don't sweat over this). If you shake the soil off the root balls, then allow them to dry out for a day or two, they will break up pretty easily. Then add the root balls and old soil to some new soil or just use as-is if you don't have any new soil.
Add:
-additional humus (ewc and/or compost) at the rate of 1 part humus to 4 parts old soil.
-additional aeration amendment: add about half as much additional aeration amendment as you do additional humus (so if you add 4 gallons of compost/ewc, add 2 gallons of aeration amendment). You may need to add more to keep the level of aeration amendment consistent with that of the original soil-go with what you think is best.
-kelp meal: 1 cup per cubic foot of soil.
-dry organic fertilizer: about 1/4-1/2 cup per cubic foot.
-liming amendment: approximately 1/4 cup liming amendment per cubic foot of soil
If you amend soil this lightly, you don't have to let it sit and cycle (cook) before using it again-just toss a new plant right in. However, if you add any "extra" amendments or more than about 1/2 cup per cubic foot of the dry organic fertilizer, you will need to let it cook for 2-4 weeks before re-using it.
At this point you can also add any new "extra" amendments that you want to add. I would recommend adding about 1-1.5 cups total of additional amendments. Remember that if you add "extra" amendments you will need to allow the soil another 2-4 weeks of cycling (cooking) to give those amendments time to break down.
Let's say that you started with the base soil amended with only kelp meal and dry organic fertilizer, and now you want to several "extra" amendments (or just one, whatever you like). Make a blend of all the amendments you want to add, using equal portions of all amendments with a double portion of kelp meal. Now add 1-1.5 cups of this mix to your organic soil and allow to cycle for 2-4 weeks, or more (the longer the better).