Some tire/rim combinations are harder to mount than others, but there are a couple of tricks to make it a little easier. I almost never have to use a tool to install a tire.
First of all, install your tire so that the last bit of bead to go on is adjacent to the valve stem. Then, when you get to the point of forcing the last few inches of tire bead onto the rim, stop for a minute and look at the opposite side of the rim circumference. Make sure that both beads are pinched in toward the middle of the rim. That will give you a tiny bit more slack and make it easier to force the last few inches of bead onto the rim.