Mix mortar in a mixing tub rather than a wheelbarrow. The shape of the tub makes thorough mixing easier. A mason's hoe with holes in the blade also makes it easier to mix mortar properly. You can mix concrete in either a tub or wheelbarrow; mixing it in a wheelbarrow makes transporting the concrete to the site and pouring it into place easier. A tub would be handy if you are mixing concrete for postholes; you could place the tub near the postholes, mix the concrete, and shovel it into the holes. If your project requires mixing more than a dozen or so bags of premix, rent a power concrete mixer. Consider ordering ready-mix concrete for any job that requires more than one cubic yard.
Common mixing tools, left to right: Cement mixer; Mixing tub; Wheelbarrow