On Noble...use a very low setting... not a loud hiss !can't remember the lbs etc....... Use a soldering tip !! and brush, brush, brush like said above........don't hold torch on the solder until its just before flowing. It will flow fast. As you are brushing the flame across the case, and as it gets hotter, you can narrow the width of your brush flame to get the joint area hot. But before you do that, you must heat up slowing the invested patty . Directing the torch just on the joint will create failure for sure. Failure comes from not heating the complete investment-and metal at the same time.
Very important !! make a small invested patty and open up a ditch for the flame to flow into. During the last stages on the investment setting up, and or after the investment sets up. If you don't open up enough, the heat will not enter and you will end up burning up your metal and checking your porcelain.
After you solder, your joint should be very dense , without pits and bubbles. If you see that, you probably used to much heat.......
Actually soldering is very easy. IF YOUR NOT IN A HURRY!!!! whether it be pre or post soldering.
Soldering NP.......I gave up 20 years ago after seeing paste joints........I bet the solders are better now.......But who cares, I would just rewax with NP