How to supply grassroots/guerrilla aforestation operation

Let's say someone wanted to plant a lot of trees. Boat forest loads of trees, grassroots/guerrilla style, urban and rural. Maintenance issues aside (not neglected, as that's key for survival rates, just aside from this conversation...) what is the ideal way to source all these trees? Small budget per tree is key because there would be so many (and, considering maintenance or potential lack-thereof, ...surely not all will survive). Hardiness is also key because...well, planting so many trees, to a large extent they will often be on their own (with nature!)

Some answers I'm thinking of:

Start a small tree nursery to provide for the plantings, and planting 'em young to keep the operation small and low-cost while also exposing trees to the harsh realities of the world in their early days. Too small and they may not have a shot out there in the cold, hard anthropocentric world. Too big and we lose those benefits of nursing them only a little and planting them small.

Spread seeds like the mythical Johnny Appleseed. This could be a good way to go with sheer volume making up for much lower survival rates than seeds germinated and nursed at home.

Spread seed balls? Germinated seeds? I don't know a whole lot about seed balls and wonder what they're like for trees and this sort of thing Looks worth more research.

I've come across impressive aforestation projects (afforestt which runs as a business, Jadav Payeng who did what I'm referring to in a rural place, other examples) and am still not sure what the best answer is. Perhaps cuttings and seeds depending on the species, as I know local examples that reforested areas single (or two) handedly using seeds and I think Jadav used cuttings from local plants. Urban vs rural may also influence which method is optimal.

Any input for an aspiring aforester would be appreciated (though I prefer the non-toxic kind). Planting trees is great just a bit costly and clunky to spread 1" diameter ones. Thanks!

From Doug and others on another tree thread, making it sound like suitable seeds are the way to go:

One possible advantage of a seed grown tree over a container grown tree (grafted or not) is the possibility of a stronger, more site-adapted root system developing. I'm not talking about disease resistance - carefully selected root stocks will usually have the advantage there - but if the tree is capable of developing a tap root from seed it may be able to grow deeper into the soil to find soil moisture and nutrients. My understanding from reading is that grafted, bareroot and container trees almost never re-develop a strong tap root.