... Are you worried about them filling up the painted tank?
My understanding is that you could fill it at home, from a 20lb tank, but not without some risk. Do the 1lb tanks have expansion or purge valves? Can't remember.
I use a curved hemostat and you can grab the purge valve with them, what you do is close valve on 20# tank, screw in adapter, screw on 1# bottle, invert the whole thing so its now upside down, I like to aim for my 1 pounder to have the purge valve in either the 11 oclock or 1 oclock position when inverted. Grab the valve with the hemostat and open the 20# bottle valve, gently pull on the valve stem and it will start "hissing", when you see the heavy "white" propane coming out, your done. close 20# valve, turn right side up and remove 1#. your done, or repeat for the next bottle. I actually weigh mine to make sure they are not overfilled to allow for expansion, a full 1# bottle weighs 870 grams.