do u have to yellow the oriental leaves before u sun dry it/?
After harvesting leaf, your task is to color-cure it. The living leaf consumes its chlorophyll, and becomes yellow, while still alive. After that, the leaf dies as it dries out, and turns to brown. That whole sequence is "color-curing". This usually occurs while leaf hangs in the shed, and requires anywhere from 1 to 6 or more weeks, depending on the variety and conditions. If the green leaf dries (that is, the leaf dies) prior to turning yellow, then we call it "drying green," and it's not likely to ever taste the way you expect. (Candela cigar wrappers, the green wrappers, are made by doing this.)
Orientals are often color-cured in the sun. Depending on the variety, the temperatures and the relative humidity, you can sometimes hang green Oriental leaf in the sun, and it will transition to yellow, then to brown. A safer approach to sun-curing is to allow the leaf to at least begin to yellow in the shade, before putting it out in full sun. I have successfully stalk-harvested a number of small Orientals, and immediately hung the green leaf, still on the stalk, in direct sun. The moisture of the stalk then serves as a reservoir to minimize the risk of the leaf drying green. (It's curious to note that if you purchase commercial whole leaf Orientals, there are often spots of green.)
After color-curing (including sun-curing) you can either allow the leaf to naturally age for months to years, or force-age it in a kiln (~125ºF at 70%+ RH) for 30 days. We usually just refer to this as kilning. Cigar leaf, for example, that has color-cured, then been kilned, can be used soon thereafter.
Flue-curing (for flue-cure varieties and some Orientals)
is not preceded by color-curing. The point of flue-curing is to yellow the leaf as rapidly as possible, then halt all further chemical changes by raising the temp, in stages, to 165ºF, all over a period of typically 5 days. Sun-curing is a poor man's version of this. The notion is to rapidly cure the leaf, in order to prevent its sugars from naturally converting to starches. Flue-cure varieties (often just called "Virginias") and some Orientals are naturally high in sugars, so this works. Most other varieties (including burley varieties) don't have that sugar, and generally come out crappy if flue-cured.
Now, your "bunker." If you use it for color-curing, then you simply hang the leaf in there, provide some ventilation, and wait for the leaf to color cure. I do that with a simple wooden shed that has an internal box fan and a window exhaust fan (that turns on at 70ºF or higher). You need to keep the 3-day-average humidity in the range of 70%. You may need to increase or decrease the humidity, depending on your weather. [Vent at night and close in the day to increase humidity. Vent in the day and close at night to lower humidity.] The color-curing takes as long as it takes.
If you want to use your "bunker" for a kiln or flue-cure chamber, then you'll need to determine a sufficient heat source for that size structure and insulation. For a structure that size, I doubt that lights are the answer for heating. Using LP is more complicated, since the combustion products must not mix with the tobacco, and need to be vented with a flue of some sort. [Gas combustion products exposed to the leaf increase the tobacco specific nitrosamines (TSNA) in the tobacco, which increases the cancer risk.] Most household oil-filled radiators have built-in temp circuit breakers that won't allow the device itself to reach kiln, and certainly not flue-curing, temperatures.
If the "bunker" wall is just 1" foam board, I don't think you can get it up to 165ºF without a massive amount of energy input.
Bob