Nowadays everybody is a specialist, and that is as true in martial arts as anywhere. In the FMA we now have knife specialists, sword specialists, stick specialists, etc. In the old days (like when I started in this art 25 years ago) the claim to fame was the versatility of technique, that concepts could be applied to any and every weapon effectively, from empty hands to staff, spear and even projectile. As GM Angel Cabales used to explain, "when it comes to 'for real' you don't have time to think about what you use." In other words, if attacked, you might have a kitchen knife or a tire jack or your jacket or your girlfriend's purse. In the end, it shouldn't really matter, because you will know what to do with it. You cannot be thinking "Oh, this is a knife so I have to do like this" or "It's a shorter stick than I'm used to having, what do I do with it?" The important things are balance, timing, coordination.
When we train with a stick or blade, what we are really learning is sinawalli, which just means "weaving." Kenpo grandmaster Ed Parker used to say the main benefit of learning an art was to keep you hands from running into each other. At high speed, that's as bad as getting hit by someone else. The better we get at weaving, the more we control our airspace, the personal zone around us. One has to have the proprioceptive sense of where the hands are in space, relative to each other and to an opponent. By training with weapons, we increase both the area we cover and the density of movement within that area, but the coordination comes from the hands.
When I practice solo at home, I often lay out a variety of "toys" to play with. I may start with a 21" stick, then go to double 30" sticks, then to a knife, do some empty hands, then a 6' bo staff, a bullwhip and finally a sword. I may flow through these one after another while continuously shadow sparring in a small room. It isn't a matter of thinking what to do; my basic patterns of movement are ingrained but I can improvise using imagination and visualization. I simply change weapons as the feeling calls for; there is no necessity to use them all. To a certain extent, the weapons teach us what we need to use them. Something long and heavy in the end, like a shovel, will feel very different from a balisong. The former may require using more body dynamics to offset the weight and balance, whereas the latter is close to empty hands, very fast and flashy.
There are three bridges to master in martial arts: legs, torso, arms. These are sometimes referred to as roots, trunk, stems and flowers. We ground our root through the feet, support ourselves upright with the spine, extend through the arms (stems) and manifest the "flowery" movement with the hands. Like a tree swaying in the wind, all parts must be connected and coordinated. The flowers need the support of the roots and trunk to flow smoothly, and the roots must feel the energy of the flowers, connecting them to earth. We coordinate the movement externally through the muscles, internally through the breath.
Three things I always emphasize; in Tai Chi Chuan these are the "3 external correspondences."
Hands and feet move and stop together.
Elbows and knees move and stop together.
Shoulders and hips move and stop together.
The other thing is to understand how to coil and uncoil, which allows us to store and release energy. All movement is based on extension and leverage; all a weapon does is extend the range and efficiency of these things.