In most reenacting it is important to have some documentation. The problem with the mid to late 18th century is that there is precious little in way or serious documentation to reference.
The original material still housed in museums is not generally on view to the public, which makes it hard for people to study them; and the vast majority of that material are artifacts from the upper class. Their personal items and clothing, made to such a high degree of quality and used so little in rather privileged hands, are the only things that survived the rigors of time or that society felt was worth saving.
Private collections in many respects are nearly worthless in historical value as references. The materials in most private hands has never been properly documented so the dates of manufacture and purpose of use have been lost to the ages and now are only rumors and guesswork... "This has been in my family for years... I THINK it was used by... I believe during the..." etc. Nothing is ever known for sure.
In my work I have had the rare privilege to not only see many artifacts that are not on display to the general public, but I have in some cases been lucky enough to hold them and examine them.
My hunting pouch is based on some sketches I made of an original bag (dated to around 1740-50) that I was lucky enough to spend a hour or so examining. Like most bags of the time, it is a simple affair with no real decoration or adornment. It was a thing to carry gun related items in, nothing more.
The leggings are the same. I have examined a few original legging examples and no design was set in stone. Mine are sewn the entire length, but I have seen some examples that were just tied together every few inches or so. The design of mine is decidedly eastern, note the 1" edging up the outside. Some people make their leggings quite large on their legs, giving them ample room, not unlike a modern pair of pants. This is a mistake of the modern mind... ::
In reality, leggings (especially eastern leather leggings) should fit tight on the leg. This characteristic is evident from the original examples still in existence. If you examine them, you will see a defined shape of the former owners leg in the material. Sweat stains, wear marks... all of these point to a garment that was being worn tightly on the limb.
The two shirts are reproductions of the common man's shirt of the time. The Longhunters of the 18th century were known to wear these types of "hunting shirts" and most reproductions made today are quite accurate, showing the same variations no doubt found in the originals of the time. Mine are based on a mixture of standard patterns available. The light hunting shirt is made of cotton muslin and walnut husk dyed. The spit shirt is a slightly heavier material (fustian) and was dyed with butternut husks to gain a slightly warmer brown than walnut.
The frock coat is made of cotton denim (not the jeans type, but the closest weave I could find to match denim of the time) and was first dyed with butternut. Then I mixed together a careful blend of both dark green and brown rit dye and boiled the frock for about 5 minutes in this mixture. I then washed it three or four times to bleed the color off to the shade I wanted. It simulates a period looking green stain quite well I think.
The references used for most of this have been from my own eyes, looking at original examples, talking with collectors and reading descriptions in journals of the time. The references in that regards are to many to list for sure, but for more of a "in a nutshell" reference I would recommend the book "Recreating the American Longhunter : 1740-1790" by Joseph Buckman. The information in this book is extremely valuable as it references many different journal entries and makes some very sound conclusions regarding clothing and equipment.
I would also recommend anything written by Mark Baker. Although I question some of his conclusions regarding the mindset of the eastern longhunter and take some of what he says with a grain of salt... his ideas regarding clothing and equipment are pretty sound and worth referencing.