I don't think if they don't have an ANN thread on bitcointalk they will have it in any other place, this is because the concept of ANN thread originated from this forum. Though if this companies don't have an ANN thread on bitcointalk doesn't mean it's not a good project, you can go through the whitepaper to see if it's a project that is feasible or not.

You can still check on google for other people reviews.