Sounds like You're getting the Lead Part too hot then dipping. Heat a little, then swish the Part in the Powder. If the Part comes out only slightly dusted, almost no paint, then heat a little longer (slightly) then swish in the powder again. Do this until You see how much to heat A GIVEN PART before swishing in powder, until You get the coat that You're looking for.
Please note, that smaller parts will heat faster so the Temp of the Part when it gets to the Powder will be higher than heavier/thicker parts because the Core of the Part will draw heat from the Surface of the Part until the Core heats up.
As the Weight changes, so should Your heating times. Small bursts of heat then swish in powder, until You get the hang of each part's weight and heating requirements.
Another thing that can be considered is the Part's distance from the heat source...I use a heat gun for coating. Use Your Thermometer to gauge the temp at given distances from Your heat source. I consider the Paint's Curing Schedule here, so I don't excessively exceed the Curing Schedule's Temperature, so I might not "burn" the Powder Paint.
Once I get a good coat I use that same general distance to set the Powder, by rolling the Part so the Heat gets to all sides...it'll get shinier as it "fuses" together on this initial coat-heat.
The True Curing Schedule is separate from this Coat-heat. The Cure Heating will achieve the Durability that is desired and beneficial, but not absolutely 100% necessary...more-so not 100% necessary if You tend to lose a lot of Parts in Fishing them.
Usually, once the Part is coated to my satisfaction, I run the Part under the heat gun for a total of maybe a minute, then Hang to Cool. This is Well-Enough, but yes, the Oven-curing Schedule DOES greatly increase durability.
