Powershell to Implement Security in 20 subsites instead of doing manually

Guys,

I have 20 Subsites which are created from the same site template.
IN lines with implementing security i want to do the following :
a. break site permissions and assign new groups
b. break list permissions and assing new AD groups
c. Use audiences on webparts
d. Use audiences on navigation links.

And there will be more that i will have to do down the line. Each site will have differt users assigned to them.

Running an estimate i would spend around 16 to 24 hours jsut to manullay implment the above security steps in all the sites. Is there any can script this use Powershell?

thanks in advance