The dull side of aluminum foil has been used by some growers with great success. The thickness allows you to easily wrap pots, cords, and anything else that eats light very easily.
I use the shiny side for "booster seats" under my plants...I wrap books in foil to raise the height of shorter plants toward the lights.
One of my two grow room doors has the dull side of aluminum foil and the lower buds lay right against it and are very happy.