I've heard of hardware store shade cloth being used as a cheaper alternative to infusion mesh.

It can definitely work. There are a few different types though and you want the woven type which can be hard to find. I believe we used to use 40% coverage found at http://www.farmtek.com/farm/supplies/prod1;ft_shade_cloth_material-ft_sunblocker_bulk_shade_cloth;pg103762.html

Excellent, I think my local hardware store has woven 30% so I'll try that. I've heard that it infuses faster along the warp direction (lengthways) than the fill direction (across the roll). Have you noticed this?