The Hot Strat I use with Unity is to just make animations in GM8, save them with that so they become strips, and run with the "_strip4" notation it uses. To improve performance a bit, I do actually go like "arrow = loadTextureStrip("System/Arrow", 5)", specifying the animation frames manually so it doesn't have to guess, but I think you could be lazy and have it load every asset in specific folders into a dictionary, then reference that using frame-count-less names. In fact that's probably a great way to do it, though ideally, you'd only actually load resources as they need to be used.