I have to say...I am a big believer it using DAP brand fun tack.
#1. YOu have to buy DAP Brand...not just any blue or white tack will do.
#2. Use a lot of it....really work it and get it warm. I use 4 balls probably the size of a quarter for each large (12 x 18 + matting) work. might use dime size pieces for smaller work. I have hung large foam boards with walnut size balls of fun tack....we have glaze tile walls in our school, only packing tape and fun tack stick to them. I could use a glue gun...but the fun tack can be recycled and once you accumulate it...(I have a ball as big a as a softball) then you should have enough to hang whatever you want.
#3. I also use fun tack to hold together those little/big clay pieces that fall apart.
Only problem.....kids love fun tack...and last year, I had my huge ball of fun tack stolen along with all the fun tack from the bottoms of works hanging in the hall.