I just finished putting 12 reinforcement patches on a tarp. Holding them in the correction location can be a task.
So I got into some of my wife's sewing stuff and found a great help. She does a lot of embroidery sewing and needs to hold fabric in position. She has some Textile Spray Adhesive that she uses. Actually she has about four or five kinds. The can says "Won't Gum Up Needles!"
I used it to spray on the reinforcement patch and then place it on the tarp fabric. I just sprayed it on the patch and not on the tarp material. I did not want any overspray on the tarp.
It would hold the patches in position so I could move the tarp to the sewing machine and stitch it down.
I hope this tip will help others in their DIY tarps.