More good input, thanks. At the moment, I'm only looking at simple, straightforward stuff, mainly numbers, winkels etc., and probably some unit badges. At this stage I'll leave the individual aircraft sheets to the big boys.
With individual numbers, winkles/bars and unit badges, it will be possible to make up whatever particular marking is required, and stencils, Werk Nr etc can be obtained commercially, or easily printed off a PC onto inkjet/laser decal paper.
It must be remembered that this is not a commercial operation, but an attempt to obtain something which is difficult or impossible to get from normal sources - ordinary Luftwaffe numbers. Although specific aircraft markings sheets would be nice, it's way beyond my means financially and logistically, just as the lack of these from commercial outlets is probably for the same reason - relatively low demand/sales in comparison with investment and required minimum order quantities.