Just thought I would post a little experience I had using an (home-made) STP.
If you use a small one (it was one with a small plastic spoon) be careful with the tissue "downstairs". I inflincted some nerve damage using it, resulting in an upsetting stinging sensation that kept me awake at night and anxious during the day.
The combination of using the STP and not going to the bathroom frequently enough, ended up giving me a UTI as well, which wasn´t severe but the combination of both crappy situations did not make me happy.
The nerve damage ended up fixing itself by not using the plastic spoon anymore.
Just wanted to warn others to be careful with it, since we don´t really want "those parts" claiming our attention.