I think there is an easy answer to it..... maybe not politically correct and it'd sure tick a few people off but the easy answer is to move every rhino out of Africa and move them to a safe place and then sell some to the chinese/vietnamese etc and allow them to farm the species just as other species are farmed. Hell, you could even let them play genetics and breed 2 headed rhino if they wanted to.
Then once the pressure is off just reintroduce the rhino back to Africa.
I appreciate that solution isn't perfect but I reckon it's the only one that'll work and if it's not taken up, my bet is we'll see the end of rhino hunting within a very few short years and the end of the rhino shortly thereafter.
On the subject of using rhino horn as an aphrodisiac, I can guarantee it doesn't work.......because I've tried it.
No matter how well you tie the darned thing on, it just falls off because it's too heavy to stay in place!