I have never advised on soil, I only like to advise on technique and what I see. So it's really up to you Grandpa.
I think coco will have amazing results but coco requires a lot more attention to watering than your go-to soil. I absolutely agree with Cultivator, you guys just have to think about the steps it takes to water as frequently as coco needs. If Grandpa can't water one day, what is the implication of that in coco. What about 2 days no water? Also, think about budget, every cent counts.
This stuff is great, layer that with the soil you already have, keep your nutrient soil near the bottom.
PRO-MIX HP BIOFUNGICIDE + MYCORRHIZAE
I think this could be what Cult is mentioning.
"PRO-MIX HP BIOFUNGICIDE + MYCORRHIZAE
HP - high porosity
With its high perlite content, PRO-MIX HP provides a great growing environment to growers looking for a significant drainage capacity, increased air porosity and lower water retention. The added benefit of fibrous peat moss and coarse perlite makes this formulation ideal for growers who require a superior-quality product adapted to their needs for watering flexibility and crop seasonality."
I put my first layer of MC on the bottom. Then soil with nutrients, then MC, then soil with nutrients, then MC and so on, layer until there are no nutrients at the top just the MC. Then I adjust with nutes every feeding.
This method will also require water, but once every 3 days, how much does coco require watering again?
Maybe research coco for your next grow and use what you have now?
Who can
donate the costs of MC for Grandpa?
EDIT: Cultivator, I know you didn't read his full journal, are you aware the Grandpa is visually impaired but smarter than all of us put together?
BTW, no rush Grandpa, this is no time for that stuff right now. hahahahaha