You could try DIY foam kits, or this method....

Here is a link that might be useful: DIY

The ma$$ive outlay to insulate with spray cans would be better spent on doing a teardown and rebuild to a design that is meant for 4 season occupation rather than something that's impossible to even kludge in a meaningfully impactful way. 80% of your heat loss is from your ceiling/roof, 15% is from windows/walls, and only 5% from the floor area. You are going about spending the most money in the least effective location to render any type of result.

The home's design is the enemy here. Without addressing that elephant, you're wasting both time and money. One way to do that is to add foam panels to the roof and reroof over that. Effectively creating a SIP by reverse engineering. Then address air infiltration at doors and windows and add insulation to the walls. All of that is far more important than anything under the floors.

Great advice on the DIY spray foam kits. Every house is different but I dont think Hollysprings % numbers are typical. Complicating the math is that the A frame roof acts as the walls in that situation. For a floor exposed to the elements and not the ground, it would probably be closer to the walls and should be insulated to the same level of the walls.

Even if those % heat loss ares were correct it would be assuming a nearly airtight structure which is almost impossible to achieve. Insulation strategies, especially the floor and roof, should first focus on an air barrier. Spray foam is popular for these locations because it does a better job than most insulations and stopping airleaks through the cavities. Dont stop at the cavites though. Seal air leaks wherever you can as its usually the most cost-effective weatherization strategy.

Ok thanks,
The initial link is something I had not thought if, neat idea. Will take a look and see if squeezing or cutting rigid up into bits then foaming seams will be feasible here.

The do it yourself spray kit found locally is $630 for 200 sq' at one inch thick, and I need 600 sq', and I thought 2-3 inches thick.
I need to either shop around further or get another plan.

bump

hate to point out the obvious, but the cost of professionally installed spray foam has dropped a bunch.

I would get a least a few bids from local contractors. If this is in a ski area, they are used to retrofit scenarios with A-frames.

I got one quote to spray foam whole cabin (below, walls and roof and there is a loft), but it was $9800 plus tax.
Then, I need to put up t&g pine. (or just drywall)
Thing is, the floor space (excluding tiny loft) is 350sq'.
Figured if that's the going rate, no point wasting other contractors time. Maybe will try another.