Any fluid, including air, will seek the path of least resistance. If that's up the sides, then that's where it will flow.
There is a myth about the "volcano" affect of powder, that you need it to get the desired coating and that's simply not true. You want the powder to be fluid, and flow, and be "fluffed" up, so it's not clumped together. So as long as you get enough air thru the powder to accomplish that, that's all you need. Those volcano's are just excess air.
Fine powders of any type have a tendency to absorb moisture, even if it's only from humidity in the air. That can cause clumping and a thicker coating on whatever your painting, as can too much heat.
You want the powder to be as dry as it can be, so keep it in sealed containers when not using it, and add silica gel packs to limit moisture. A lot of fluid bed problems are created because the powder is not as dry as it should be. Unfortunately, the only way to tell is visual based on how fluid it appears. Moisture content can be measured, but it takes appropriate test equipment to do it and most folks who paint lures won't have it available.
Fine powders also have a tendency to compact, particularly with vibration, so keeping it stirred is essential. However, in a small fluid bed cup it's also possible to be compacting the powder some depending on what you're using to stir it. Ideally, you only want to keep it fluid. So, a tool that stirs but doesn't compact is what you want. A spoon for example, may not be a good choice. A stout wire may work well.
The fluid bed I use has 4" diameter cups and are about 4"-5" high, with porex filters in the bottoms. I get very good air flow with an aquarium type air pump. Each cup will hold about a half pound of powder, without overfilling, and I don't get the volcano's too often, but I can tell when the powder is fluid. When the air is adjusted properly, the level in the cup rises up about a 1/4". I use a stir that is a heavy wire and has a looped end, so it won't compact but will stir up the powder. I don't have much problems with getting a nice even coating when painting most jigs, and I powder coat jigs from 1/100 oz, up to 20 oz. When I do have problems, it's 99.9% of the time heat related.
When I first started using a fluid bed, I believed that stuff about the volcano's and was using a larger air compressor with oil & water traps and a regulator in the air lines. Even with the slightest amount of air, it was too much. I was blowing powder out of the cups trying to get that "volcano". I switched to the aquarium pump that I use now, and found out that the powder was fluid enough, with minimal air passing thru it, and that as long as what I was coating was within a good temperature range, I was getting nice, even coatings and no drips when I would cure them.
I do have one powder that no matter what I did, I would get a coating that was to thick and would drip during the curing. I use an oven and set the temperature with a calibrated thermometer, and have a diffuser to keep direct heat from the heating elements from causing hot spots. I still got problems with that powder. I finally figured out that it was due to excess moisture. That powder was the oldest that I had, and I had not taken necessary precautions to keep it dry. Lesson learned.
If I get dripping with any other powder that I use, it's been because I had the oven set to the wrong temperature. Powders have a recommended cure temperature and time frame, and that temperature is for the material that you're coating. So if the cure temp is 400 degree's for 15 minutes then the lead needs to get to 400 degrees and stay there for 15 minutes to obtain a proper cure. But, since powder coating was not intended for fishing tackle to begin with, and was intended for coating much larger areas, sometimes you will have to make adjustments. It's one thing to coat a sheet metal panel that may be several square feet in area, and another to coat a jig head that may be less than a 1 square inch in area. All powders are not the same either.
So, be sure to keep powder dry, and fluid in the fluid bed and stir it frequently. Then make sure your heat is proper for the size of what it is you're coating. Following these suggestions should give you the best coating and most durable result when cured properly.
Here's a few jigs that I've powder coated.
