First of, you could probably do this with any scale, but it seems to work better with 28's. Given the abundance of ImagiNations that have sprung up over the last few years, and the fact that many people would like to also use these figures in convention games, campaigns, or just historical re-fights with their clubs, it may prove handy to you.
One qualification: I probably wouldn't do this with purchased flags like GMB or the Flag Dude, unless I just really had a lot of money. I would restrict it to self-created flags.
So, paint up your unit however you wish (although you might take some historical precendent into account), and then consider all of your options for the unit from a historical perspective. For instance; red coats without turnbacks, blue cuffs and waistcoats, white gaiters. They may be your "Duke of So-and-So's Royal Guard" with a magnificent standard of your own creation. But, if you prepare and mount that standard with this method, those self-same troops could become the following with the right flags:
The Gardes Irlandais in French service at the turn of the century;
The Irish Regiment Roth in French service in 1718;
The Irish Regiment Ultonia in Spanish service in 1709;
Any of several Swiss Regiments in French service to 1720;
The British 27th Foot, Coldstream Guards, the 9th Foot, or the 18th Foot, around or after 1712.
And I'm sure that there are others that I'm not thinking of right now, and that you will think of. Now, all of their "small clothes" might not be an exact match, but you can decide how closely you want to scrutinize that. I would recommend painting drums rather abstractly; don't go into too much detail on the Regimental arms or crest, as this will stand out, keep it deliberatley simple and abstract.
So, here's our tip: Find a good brick and mortar shop that specializes in Model Railroading, or a web site that does and sells retail. A physical shop is better at first because you can buy single pieces of everything. Later, if you like the technique, then go online and order in bulk. To start out you need 1 piece of 12" long white Plastruct rod, 1/16th inch diameter. You will find that it has a wire center that is 1/32nd of an inch diameter, and that the plastic outer coating can be removed with a little craft knife work. You will also need 1 piece of 1/16th inch OUTSIDE diameter aluminum or brass tubing from K&S or similar supplier, you will find that it is hollow and fits over a 1/32nd inch wire or rod.
First cut a piece of the Plastruct rod to the overall length that you want your flagstaff to be, not counting any topper. Then measure the distance from the BOTTOM of your standard bearer's hand to the base or groundwork and mark this distance on your plastic rod. Remove all the plastic coating from all of the rod EXCEPT the span between the hand and the ground. Attach this "flagstaff" to the figure, either in his open hand or by drilling out the hand, leaving the 1/32nd wire at the top, and paint the coated portion as you wish. Now cut appropriate lengths of the 1/16th inch tubing to fit the exposed portion of the staff. Leave the wire portion unpainted and put just a slight "bend" in it, not really enough to show, just enough to provide friction to hold the standards on.
When you cut your tubing "toppers", remember to leave enough length to allow for flag toppers, tassels, cravattes, etc. Also, when you design and print (or paint) your paper standards, leave a slightly wider "gap" or "gutter" between the two halves of the flag to go around the 1/16th inch tubing, about 3/16th of an inch should do, but you can make it a little wider. Simply attach your flags to the tubing standard "toppers" (you can even make a simple wire jig to hold these while you work on them), shape and furl your flag as you normally would and varnish or coat in your usual manner. Finish off any exposed edges of flag or tubing and you should be done. Your new flag should slide onto your "base" staff with only slight finger pressure and the friction from the slight bend should hold it in place and facing the right direction.
Between games, if you can round up some old plastic "button boxes" or even those metal tins the Altoid mints come in, just store your spare flags between sheets of toilet tissue or thin lint-free cotton. Then, depending on the game or scenario, simply whip out the correct standard for the event, slide it on and rally your troops! While I directed this at the 18th Century and ImagiNations, I've also seen it work with mercenary forces for Late Medievals, the Italian Wars and the Thirty Years War. Need to switch sides for a scenario, just switch flags, little fuss or muss. Hope this is useful to some of you out there.
Bill