Portal 2

You get the cheevo once you reach the exit of the level. Cant be missed. Hit the switch and place a blue portal under the gel dispensor, use random orange portals all over the floor to cover area in gel. bounce around blue gel placing orange portals to get gel on ledge one level up. once higher use gel to bounce over to cross room to force field. place orange portal on diagnol target spot to spit gel across to where you just came from, replace blue portal under gel dispensor, you will see gel land nearer the exit. place orange portal on diagonal spot and drop onto portal your firing under yourself to bounce on gel and reach exit.
Sorry for bad solution or explanation but first ever guide...