You can usually buy denatured alcohol in a can at a hardware store. Heet gas line antifreeze works but has lower heat content. Most thruhikers build their own stoves. There are numerous designs on the web, normally they break down into two types, self pressurizing or non pressurizing. The self pressurizing units allow the alcohol to boil and form jets of flame, they tend to be faster. The non self pressurizing units are usually a open can with some sort of insulation that allows the alcohol to wick, its the equivalent to heating with a can of sterno. Trangia is a non pressurizing stove that many folks buy. One thing to consider is that the stove is only one part of the system, generally you need a pot support and the better designs incorporate a heat shield that wraps up around the side of the pot. These tend to be custom to the pot being used.
IMHO
There are constant debates on what type of stove to bring on an AT thruhike on whiteblaze.net. The person I sectioned hiked a large section of the AT with switched to alcohol, I tried it once and decided to switch back to a cannister stove with a custom heat shield. One thing that neither one does well is frying as the heat source is concentrated and most backpacking cooking gear is thin.
A broad generalization on my part is that a alcohol stove is great for heat and eat meals, bascially heat water to boiling, dump in pot, pouch or ziplock bag with ingredients, stir, then either eat immediately or store it in an insulated pouch (AKA cozy) and wait for the cooking to be completed. So if you buy prepared dehydrated food its a good fit. It typically takes longer to boil than a cannister. Most thru hikers tend to get down to eating food as fuel, where they go for the maximum calories with the minimal hassle
A cannister stove can simmer which makes it easier to cook somewhat more complex meals that requires an initial boil and longer simmering. With some work, they can be adapted for use with an outback oven (for weekend use where weight is less of an issue). With a custom heat shield, my cannister stove works well in breezy conditions. I also have used my cannister stove as a supplemental heat source for heating water bottles for my sleeping bag in unusually cold weather. If I am willing to use up fuel, I can heat a lot more water a lot quicker with the cannister. (Note my rational is that the additional fuel carried is less than the weight of heavier gear). By the way, finding cannister fuel has never been an issue wth me, the biggest pain is using up the partially full ones.
