I'm in the process of retightening my locs, using a metal yarn needle. (I used pliers to widen it a little in the middle). I tried to get a micro sized LOC-KEY very similar to nappylocs tool, available here(UK),but in the end I decided a good ole yarn needle would do the job and indeed it's working alright. The handle is a little longer than I would like, other than that it's doing OK.
Now this (DIY)ReTi business. Whoever said it's not rocket science is right, but the potential to join locs and do the wrong rotations is HUGE. I've joined 6 locs and then spent a great deal of time un-joining 5. I gave up on the last one and just joined them. The thing is to make sure the loc to be tightened is ISOLATED- clip everything else out of your finger's way. I did most of the front using a mirror, but the back I'm doing mostly by feel, and that's when thing can go wrong. The advice is, do a little bit at a time. When you accidentally join locs, take a deep breath, rest for a few mins, pray, and then try to push the loc back through the gap you pulled it through. So far I've completed 3/4 of my head in 3 days doing a few sections at a time. I'm using a 3pt rotation which is supposed to be 12,9,6,9. Instead I was doing it backwards,but I've now settled on the 9,6,9,12 bc I find it the easiest on my arms and fingers. I hope to complete it today or tomorrow and will update when I'm done.