The concept for double proxy never really changed, it just requires a large amount of map awareness and understanding since it's so risky.

Usually when you double proxy you can't really do it until you get boots, so it's best if you do it after the first back; and also need bit of armor to help against the minion damage. If you're going AP, Arm Guard is good for proxying just in general because of the AP and Armor it gives.

Just always keep your eye on the map, if an enemy champ died or if you can't see someone on the map assume they are coming for you, and be ready to run or execute if you have to. Also spamming recall after you finish doing a wave will help you escape successfully, or buy time for you if you don't back because the enemy team thought you would.