Personally, I set up every project with its own source, tomcat, database, etc. even if it means duplication. These days storage is cheap and makes this possible. Of course your milage may very but I thought I'd share my setup with you.
I have a project directory with all my projects which looks like so:
/projects
/foo-project
/bar-project
/my-project
Inside a project I have
/my-project
/tomcat
/bin
/conf
...
/src
/portal
... my portal source ...
/plugins
... my plugin source ...
/portal-ext.properties
- I then setup tomcat to use different ports (8080, 8081, 8082, etc...) so that I can just leave them all running if I have to or want to.
- I setup Liferay to use different database for each Liferay instance.
- I place the
portal-ext.properties
as a sibling to the tomcat directory and Liferay will read this file (assuming the default behavior). This offers quick and easy edits as well as figuring out how you've set each project up.
The advantages should be clear. You can just "walk away" from a project and into another without tearing down and setting up. And when you return everything will still be as you left it. Context switching is also quicker and helpful if you want to answer a question about a project you're not yet working on.
Depending on the complexity of each of your projects, multi-instance might not work for you. Hooks and EXTs may conflict with each other and it appears as if this is already the case with your projects.
If you can afford the space (which is not much) this has been the fastest way I have found as a Liferay developer.