Agreed. I do green manure with kitchen scraps but mostly soft things like leaves and eggshells. I freeze it first so it breaks down faster and it takes a while for me to collect enough. I dig a hole in the soil about 18 inches deep and trench compost the kitchen waste and maybe some yard greens that have been chopped up. I avoid meat waste. Bury the trench and I usually have to cover it with a board or pots on a board for a couple of weeks. It keeps the mongoose from digging it up for the grubs. The soil will sink as the vegetable mass loses water then I can remove the board and level the top.
I probably should clarify the earlier post. The compost that is mixed with the soil should come from a variety of sources not one like "forest products". Compost sources should be from at least 5 sources like kitchen waste, mushroom compost, composted manure, leaves, garden waste (non diseased plants). I did not mean for the raw materials to be used but the sifted compost made from a variety of sources like the ones mentioned.
Making your own is best but it means planning at least 6 months ahead and starting a compost first.
Buying in bulk is a good option.
You can get manures from farms and stables but they will need to be composted first or nothing can be harvested for 120 days from the time the fresh manure is added because of pathogens that can be in the manure. Manures are also high in salt
You can get a truckload of chipped greenwaste if you ask the local landscapers to drop a load when they are in the area. Most would be glad to do that to avoid the cost of hauling it away and the tipping fees.
You can get a truckload of compost and other materials like sand, topsoil at some greenwaste facilities. It is usually cheaper if you pick it up. The trucking fee costs more than the product.
A bed that is 18 inches deep would be sufficient for most plants and require half the fill. Unless you are doing hugulkultur then you could fill the lower part of the beds with rotting logs which will decay over time.
Happy gardening in Hawaii. Gardens are where people grow.