Yes tank matters. The larger the tank, the longer it can put out that blast of air at or near 150psi or whatever the maximum pressure it's rated at. Obviously the higher the pressure the better as well. If you are buying an air compressor, make sure you buy the quiet kind too. Your wife would hate you if your noisy air compressor kicks on at 2am in the morning.

But let's get back to the basics. Are you using soapy water to help seat the beads? Are you using the inner tube trick to seat one side, and then use air pressure to seat the other side?