Remove the clothing as soon as possible after detecting cactus thorns in the fabric.
Situate the clothing under bright light to examine it carefully. Stretch the fibers across the grains, if possible, to see where the thorns have embedded themselves in the fabric.
Hold the magnifying glass over the fabric to enable you to see the clothing better.
Grasp the ends of thorns you see with the tweezers. Pull gently but firmly to extricate the thorns from the clothing completely. Take care not to break off the thorns as you pull them from the fabric.
Place the thorns on the piece of white paper so you can see them clearly as you remove them. Do not lose track of the thorns you remove or they may become embedded in clothing or skin again before you dispose of them.
Continue examining the fabric to find every thorn. Doing this may take time -- many thorns may be embedded in the fabric. Remove every thorn you find.
Wrap duct tape with the sticky side facing out. Press the sticky tape against the clothing to remove tiny or stubborn thorns from the fabric. Continue pressing the tape to the fabric to remove as many thorns as possible.
Examine the clothing again with the magnifying glass to see if any thorns remain. Pass your hand over the fabric lightly to see if you can detect thorns in the fabric. Continue working until the clothing seems free of cactus thorns.
Fold the paper carefully to enclose the thorns. Dispose of the paper and the duct tape cautiously when you finish removing the thorns.