I have done this and have been in the same situation with trying to edit pixel by pixel.
one point that comes to mind as there are two types of drawing programs, vector and pixel graphics.
.jpg or .bmp files are bitmaps, which display the data in pixels. so the data is basically telling the program which dots to fill in. Vector graphics on the other hand could display a border by width and position, length of it’s sides, radius of corners etc. the advantage with vector graphics is that they can be resized without loosing clarity. I would try to work with a Jpg or similar but if you want to say, draw a circle , if there is a circle tool it may help it look more concentric. you can type and drag letters around but when you save the image it will likely conver the type into a bitmap image and you may see some distortion of the letters from this.
when you start the image try to think of the end result, as far as size ,resolution, and number of colors. something to be printed as a one off should have the highest resolution your output device can use. check your printer to see what that is. Slow printing speed isn’t an issue for one or two. as long as you computer doesn’t choke on the file because of it’s size.
When you are doing things like resizing ,rotating, saving, it takes lots of ram to do that with a big high resolution file, so you don’t want extra image size or it just slows your computer down. the more ram you have the better. save backup files as you go so you can go back if you mess it up.
One thing I found is important is the paper. The real photo paper has a good finish, and is I would think fairly dimensionally stable and less likely to warp from humidity etc. If you buy photo paper, check by holding it up to the light, a lot of it has a watermark type logo that is only visable when held up to the light and you don’t want that to show up by being backlit by the dial light. I did a couple on my inkjet printer that looked pretty good to me but I think they would look better with a color laser printer. you could save the file and go to a local print shop or copy shop to have it made.
Most large print shops have proofing capabilities. When a printing job is ordered they often do a "contract proof" this is a proof made as a one off to represent the final printed product. If you were ordering a large print job you might want to first approve the color, position etc. the contract proof is approved before you invest the cost of the printing job. These contract proofers can put out terrific quality images but i am not sure of the cost. sign shops might have some nice equipment as well.
I found some waterslide paper that supposedly can be printed on and then soaked in water like the labels found in model kits. I found it at one of the stores that sells to the model train crowd. I haven’t tried using it yet but thought it might be good for labels like tone, volume etc.