I haven´t got myself any tiles yet, but I decided I have to try it out, so a couple of days ago I used some plastic pieces (round, used for placing beverages and glasses on), and squeezed together with my hands. Since my arms got tired, I could do about 3 min in a row, rest a little and then 4 more sets. The temporary width increase was awesome, although this was just a light test of the real thing!
Got some pain though during the set, but that could have been from some irregalutaions on the surface of the plastic things I used.
Gotta get me some tiles now!