I also have been soldering for to many years to count. I have found that the biggest error made by many who say they can not solder is that they are either using to small (to low a wattage ) iron or not having the items to be soldered clean. Use of the proper flux is also a big aid in getting a neat joint. Depending on the mass of the item being soldered, the size of you soldering iron tip is also important, for larger items such as a Deans connector, you need a fairly large (large mass for heat retention) tip.