I built a fluid bed with plans from TU. I used coffee filters and seems that the powder seems to have spikes in the paint. Is this because of the filters? Should i use a paper bag? Also the paint cup is 4" deep by 2" pvc pipe. Seems hard to see the paint and if i turn the air up a cloud of paint comes up. Should the cup be shorter? The color of paint i'm using is black if that makes a difference.