With paints, so much depends on anecdata and personal experience. I know some people who swear by Krylon, even though I had so many issues with them a decade ago, I haven't used it in years except in small applications where I've had no practical alternative. Some people have had issues with RustOleum, and that baffles me, as it's been nothing but consistently awesome for me for years. Some people
only use DupliColor, or
only use Montana Gold, or
only use Tamiya acrylics, etc.
With spray paints I try to use the same brand, to avoid reactions. As I said above, RustOleum has been my go-to for a long time. For most things I start with their (gray) high-build automotive filler primer, several coats. Once that's sanded down, I use either their black or white primer -- the opposite of whatever I want to end up basecoating. Then I spend a loooooong time sanding that down with 220-240 grit. Then I do a layer of white or black -- reversed from the previous layer -- and do the same. By this point, it's something like five or six primer layers and most of the minor defects are filled and smoothed (any significant ones I filled before any primer, or after a first filler primer coat has revealed them), and, once I know I've gotten things pretty well leveled, I do one last primer coat in that same color or one of my less-used ones (like gray or terracotta), dependant on what color I'm going to be painting the thing. That gets smoothed with 400 grit or finer.
(Note all this applies to macro objects like this. For models and minis, once I've got the surface clean and prepped, it's a single layer of Tamiya's fine-detail primer.)
So I've never used Home Depot's brand, and I've never had any issues with my RustOleum stable of rattlecans. I've never run into the problem you have, so I don't have any advice... except maybe to try another brand...?
I love RustOleum's reliability, because it lets me use all the primers -- for the surface-prep technique above, and for the primer that best suits what the base coat will be called on for. As I said over in the other thread, more translucent colors like reds and yellows, I prime white. Otherwise, they tend to look muddy. I'll often prime gray under black, so I can be sure of coverage. Reverse that for grays. I only use red and brown primers under wood effects, since I base coat those in shades of brown, usually. For this (or your) power armor helmet, this will mean the final primer layer will be gray, the base coat will be RustOleum's Professional Grade black. Their P.G. enamels -- at least, the black, white, and gray ones -- have ground up ABS dissolved in suspension, so when it's fully cured, you've basically coated whatever you painted in polished ABS. This is great for Stormtrooper armor... and also for the foundation for metal effects, as those work best with a smooth bare-plastic finish.
Which I bring up because I do subtractive weathering. The game lore says the T-51 armor was plated in silver to boost defense against laser weapons, so a nice polished silver is what's going to show through where the paint's been worn or scratched away (or rather, masked off).
Then I'll do white primer over that, to show the red and white main colors up nicely. I'll blackwash, but sparingly. I'll be interested to see our two repaints of the same helmet side-by-side.