I agree that the Hayes tanks are the best, but if you must use the brass tubing type, here are my suggestions. Cut the tubes to length required by rolling the tube under an exacto blade. Clean the inside of the cut end with the same blade (since it's now too dull for wood cutting). Use a pipe cleaner or rolled piece of paper towel through the tube to clean out the filings. Bend as per above suggestions. Use WD-40 to lube the tube as you slide it into the stopper. Push it in with a wood block, not your fingers...ouch! Lube the stopper with WD-40 and slide it in. The WD-40 will dry and help secure and seal the tubing and stopper.

Paul