Les -

The method you describe is used quite a lot by a small group of professionals called "kidnappers." You cut the letters out of old newspapers and paste them onto the "ransom note."

A little more seriously - the hobby/art shops, and some office supply stores, probably have "stick on letters," adhesive backed, that you can peel off of a sheet and stick where you want them. If you're not fussy about letter size and style, the lumber yard probably has very similar sheets for making address labels for your mailbox.

Some similar places should also have "stencils" in which the characters are cut out. You tape the stencils down and then spray or brush paint "in the holes." Lift off the stencils and your lettering is pretty much done. (The stencils are popular for making borders on walls when you repaint the bathroom, but the ones for that use tend toward flowers, ivy, scrollworks and the like.)

You can also use your printer to print what you want, trim it down to a "sign size." Glue it on, and then (when the glue is dry) paint over it (brush or spray) with a clear varnish or lacquer. This method is called "decoupage" in the hobby shops, and any Barnes probably has 300 books on the method - or you should find lots of descriptions on the web.¹

Note that things you print on an inkjet printer are NOT water resistant, but covered with a suitable varnish/lacquer overcoating they should be durable enough. Most inkjet inks also do fade some in sunlight, but within reason that just makes your artwork look "ancient and impressive."

¹ The "creative little old ladies" who support the hobby shops like decoupage a lot, but they like to be "creative and original in the same way as everybody else" so there should be lots of discussions in the bookshops and on the web if you look a little.

John