From your actual question, no you can use solid carbs or fast carbs and protein shake. Just make sure your carbs are right for the slin taken. I use both and switch it up but I've also assessed a tolerance level between how many carbs per iu and how fast a certain amount hits so the GI on different types of carbs needs to be taken into effect depending on when your going to eat next.
To play it safe, use dextrose or Karbolyn after slin shot.
I agree with what Green has said here also and think it correlates to you. He is saying, Keep your diet normal to what your used to pre workout. So if you take in 50 grams of protein and 100 carbs then your safe zone is to take 10iu.