I've done this and it works pretty well. I made my own funnel out of a bottle and some fuel line. The fuel line fits over the valve stem perfectly. I kind of "pump" the tire by leaning on it to "burp" it.
I haven't loaded any of my tubed tires yet- i think I only have one or two sets still tubes. I generally break the bead and pour it in. Fast, effective, and easy. However, if it is a wider rim (8.50) it can be a challenge to reseat the bead.