[GRASS-user] using USGS chunked TDDS orthoimagery

[Michael S]

I'm a non-GIS professional, I've spent the last couple of weeks familiarizing myself with GRASS and by extension the world of GIS. So far I've mainly been exploring using GRASS to overlay various types of correctly-projected map drapes onto a DEM.
I've downloaded the chunked 0.25m resolution USGS orthoimagery (Ortho TDDS) for a given quad; it comes in 90 zipped folders. I've unzipped them all and now I'm struggling to figure out an efficient way to bring them into a given location, ideally to mosaic the orthoimage tiles together, and then export the 90 tiles (or mosaic'd) raster to some commonly-used format such as PNG.
I see that I can individually import the JPEG2000 files, but this is very tedious as each tile requires import and then composite of the three bands to RGB. Mosaicing together four of these at a pass using i.image.mosaic produces very unsatisfactory results; the resulting mosaic looks completely washed out with only some of the labels making it into the final image.
Each folder has a .shp file; I can import two of the 90 as ESRI .shp, and then I see in the Map Display that my DEM image is completely covered by a grid, each with small "x" in the middle. I then attempt a vector-to-raster conversion (v.to.rast), but I'm lost figuring out the parameters; "Source of raster values", as well as "Name of column" and "Name of color definition column" under the "Attributes" tab. I've done trial-and-error and nothing produces a raster image of the aerial photography that I'm looking for. I can certainly read the column names for the .shp file, several of them I can intuitively figure out, but I can't find any documentation to guide me in this regard.
There is precious little documentation (that I can find) at usgs.gov regarding the files contained in each unzipped folder and how to use/manipulate them; anything I have found is frustratingly vague. Likewise, extensive web searches have not turned up any clues as to how one can use GRASS to use this chunked TDDS orthoimagery. I would appreciate whatever constructive guidance could be offered about this, thank you. 		 	   		  
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