You should think about creating doorway pages only as a last resort. You can do that, but you may get a higher ranking if you allow the search engines to spider your doorway pages by following links to them, rather than by submitting them manually. Furthermore, the search engines also take a rather dim view of pages which only contain outgoing links to other pages but do not contain any incoming links from other pages. The search engines will often recognize these pages as doorway pages and may penalize such pages. The solution is to create hallway pages.
Hallway pages are pages which contain links to different doorway pages.
What you should do is to create a hallway page for each search engine. The hallway page for a particular search engine would contain links to the doorway pages for that search engine. Firstly, let's see how you should name the different doorway pages. For optimum results, the file names for the doorway pages should contain the keyword that you are targeting with the individual words of the keyword being separated by hyphens. Furthermore, there should be some way by which you can identify which search engine you have created that page for.