I won't ever decap before cleaning. If you are using a regular vibratory cleaner with simple corn or walnut media...those primer pockets STILL won't get clean but you will end up with media stuck in them. And if you don't find each & every little nugget of media stuck in them, you'll eventually displace or snap a decapping pin.
Of course, if you are sonic cleaning or wet tumbling with steel media or some such thing, disregard the above.
I've never bought a universal decap die -- but I screwed in the "never used and I will likely never use it!" sizing die from a see of 7.62x54R dies in to my old single stage press (that also never otherwise gets used) and I use it as a "universal decap die" any time I feel the need to decap something.
It's not that I recommend using some obscure rifle cartridge sizing die...
It's just that I had one, it works just fine, and I doubt I'll ever use it for it's intended job.
Attention Brass rats and other reloaders: I really need .327 Federal Magnum brass, no lot size too small. Tell me what caliber you need and I'll see what I have to swap. PM me and we'll discuss.