In a way, I think the hardest part about a Gaelic polytheist/animist faith is that there's no clear way to practice. All of the mythology, folklore, and general folk practices come centuries after conversion, so if you're trying to find a clear, hard way that pre-Christian Gaels honored their gods, you're gonna be shit out of luck. That said, there's a heck of a lot we can learn from what we do have, and there are some things we can say seem pretty likely to be right on the money (ancestor veneration, ritual offerings, etc.) and other things that were clearly very recently concocted as a marketing ploy (Celtic tree alphabet or whatever the fuck). Which means that there's no one, right way to practice a Gaelic faith. A lot of it is up to the practitioner. And honestly? I'm okay with that. It leaves room for innovation, for development of personal traditions. And so long as you're clear about where each piece of your practice is sources from (ie. which things are taken from which lore, which are personal innovation, which are inspired by folklore, etc.) then, in my mind, there's not really an issue if it isn't all entirely descended from verifiable historical sources.
It does mean you have to be able to make some personal decisions, and it also means that group practice becomes difficult. You're gonna have much better luck putting together a neowiccan coven than you are a regular group of Gaelic practitioners, largely because it's going to be much easier to find people who can agree on sources and structure of a neowiccan practice.
Yes, there are times when I wish I had more concrete traditions to fall back on. At the same time, I would hate for there to suddenly be some GaelPol pope dictating my practice. What's challenging about GaelPol is also what's beautiful about it.
