to realy target the rear delts specifically, i like this cable move:
stand between the overhead cables, but without any type of apparatus attached to them, facing the opposite direction you want to look, grab the cables so that when you turn arround they will cross eachother. dont have any grips on them, just hold the cable at the part where it has the plastic bushing that has a clip after that. if you use the regular cable grip like for most cable moves, you will loose the correct wrist motion needed for this exercise.. now stand with the cables crossed, and put your arms staight forward, elbows locked (this should not be a problem as you wont use much weight for this exercise). now squeezing your rear delts, move your straight arms out to your side (so you would look like the letter 'T'), the cables should create an X that you want to keep right about at center eye level
hope i described it good enough, but its a more advanced move i dont see people do much, let me know if you need better explanation
i think it you want to bring out your rear delts it might be best to use this exercise first in your shoulder routine, to pre-exhaust the rear delts, then do behind the neck press, then regular press
it is a similar move to using the peck deck in reverse position, but i highly prefer this move and think it has helped me a lot more