I had been using GFO in mesh bags. I used to dip/soak them in fresh RO before inserting them into the sump for 30-40 minutes. I bought a really nice NextReef Solid Media Reactor and now I insert the BRS GFO into the reactor with a funnel. I didn't see a good way to "rinse" the GFO like I used to do when I dipped the mesh bags in RO water, so what I do is run the pump on the reactor and I direct the output hose into a waste bin I use for holding messy, wet things from the aquarium, until the water turns almost clear (about 30-45 seconds).
Overall, the cloudiness won't hurt the tank; it just doesn't look good for a while. Also, I found that after the pellets of GFO broke down and slipped through the tiny holes in the reactor, they would exit the reactor and were dumped at the base of the skimmer, so the skimmer was sucking them up and collecting them in the bottom of the skimmer. This really degraded the skimmer performance, so I placed a thin, 100 micron filter sock over the outlet tube of the reactor and replace that every 2 weeks or so.