NO!!! why do vets still recommend salt to induce vomiting?!? So old school.... and very dangerous. I would find a new vet fast.
Salt can mess with sodium levels in the blood.
Give him plenty of water. You can try hydrogen peroxide to make him vomit, but be warned that can cause gastric ulcers. Usually a lot safer than salt though. Give him 1/2 a cup, and then another 1/2 a cup in 10 minutes if he doesn't vomit
~Emergency Vet Tech
Berlin vom Spartanville 1/13/13
2008 - 7/23/12
"Take this trouble from me: Make sure my shepherd dog remains a working dog, for I have struggled all my life long for that aim." Max Von Stephanitz