The technology of animating player`s arms for holding weapons

We need to make the player's use weapon:

1. To take it out, hide it, reload it (each kind of weapon).
2. To make hand positions for every kind of weapon (shooting or not).

Since several days I've been trying to comprehend the interaction "player<->weapon". As the result I found out the following:

If we make hand positions for weapon using ArmThread, then what about transition? As far as I see, there is no such thing in ArmThread. Then how can we make "taking out of weapon"? Or maybe ArmThread is used only for "look"?
It's possible to make animation using ActionThread. Transition does work, but the one animation "covers" the another one. F. e., in a "sitting" position, the animation "reload" begins to perform, but instead of "sitting", the player "stands up", "reloads" and "sits down" again.
More probably, it's necessary to use only upperBody, but the question is How? Deleting all the keys for all the bones, trying to fix ".cfg" (maybe bad try?) expect arms/hands, gives the same result.

Does anyone have any ideas?

Thanks anyway.