Yes, exactly. Just drop a chip of wax about the size of a marble onto the surface of the melt. Be ready to stir it in thoroughly with a long-handled spoon or ladle. Also be ready for the wax to catch fire and flame-up for a few seconds. Keep stirring until you see a bunch of powdery black crud floating on a surface of silvery, shiny metal. Skim off the black crud, and start pouring. When you add more lead or ingots, you should flux again. Only takes a minute or less, but avoids a lot of frustration later on.
A basic rule-of-thumb that virtually all highly-skilled lead pourers adhere to is:
Head-off any problems before you start pouring. Fluxing is an integral part of that strategy.
After fluxing, you should see that the melt has a smooth mirror surface. It certainly should help your pouring go smoother, as long as you're doing everything else right. I used to pour a lot of salmon balls in 1.5, 2, and 2.5lb sizes. By removing the lead oxides on the surface, and making the melt less likely to form oxides, fluxing will help make sure the metal is as fluid as possible, so pours go easier.
But please read up on fluxing before you do it. There is plenty of info here if you do a quick search for "flux".
Now, as far as helping the lead molds release the lead castings, well, that's a different issue. First, inspect a cooled cannonball sinker from your 'sticky' mold, and you'll likely see some scuff or scratch marks along the mold part lines. There's a burr on the mold edge that's causing those marks, and that's your culprit. Locate that area on your mold, and file, scrape with a knife edge, or sand down the offending burrs. There may be several, and they may be small, so search carefully. This problem is very common on large cannonball molds, as they often see a lot of hard use and abuse-- but the good news is that it's fairly easy to fix.
Also, be sure to smoke the mold cavities thoroughly with a sooty flame (again, part of the "avoiding problems before they start" rule). This will help with both fill-out and mold release. These several changes to your pouring practice should make a big difference for you. Let us know how it goes.
Hope this helps, good luck!