1. Start with loose, mostly unexamined metaphysical principles.
2. Take note of what intelligent agents can do.
3. Examine the world for that which looks designed by an intelligent agent.
4. Assuming such a thing is found, identify communications that seem reasonably from the agent.
5. If the agent identifies as God/supernatural and seems trustworthy, trust them.
1. Start with tighter, more well-thought-out metaphysical principles.
2. Examine the world and how it operates.
3. Take note of what most be true about the world given how it operates + its principles.
4. Note that God/the supernatural must exist necessarily.
5. See if any communication from this God exists and seems trustworthy, and (if so) trust it/Him.
I'm not convinced that the ID proponent necessarily accepts naturalism and a personalistic God from the outset, as is often the claim. I do agree that the ID proponent's reasoning to God is sloppier and probablistic, but it's also easier for most people to grasp.
The Thomist approach requires a good share more discipline and reasoning, but is more powerful once you have a general grasp of what's going on.