Hi Albert,
Don't hesitate to ask. This is the right place for trivial or not trivial questions.
imx-test is the newer test package, so if your BSP already has the imx-test package, please use this one instead imx-misc.
The prep option only unpack the package at rpm/BUILD/<package folder>, so to install a specific package you have 2 options:
1 - use prep, scbuild and scdeploy as mentioned before
2 - use: ./ltib -p <pakage name> -f (it will prep, build and deploy in a single command)
If you want to clear, you can simply remove the folder rpm/BUILD/<package name> . It will not clear the content of your rootfs.
Rgds,
Rogerio