The ways to reduce inhibition are:
1. Choose the 'generous' options in the Sex dialog. This can reduce Inhibition to a minimum of 50.
2. Use the Mind Control option to change the person's clothing to something skimpier than they normally wear. This will reduce their Inhibition by 1 each time they see you until it reaches a level where they'd 'naturally' wear that outfit. This can reduce Inhibition to a minimum equivalent to the lowest level outfit that they have available.
3. Use Mind Control to Suppress Inhibition, which will reduce Inhibition and reduce Corruption by an amount every day. This has no limit.
4. Use Sympathic Link to Create a Link between another emotion and Confidence, and preferably Lock that Link. This will make it so whenever you improve the emotion you chose (you can choose between Trust, Love, and Lust), you will also reduce their Inhibition by 1. This has no limit.
Options 3 and 4 are the fastest; Option 3 requires less input from the player to make it work, but will also reduce Corruption. If you *want* the person to have high Corruption, you'll want to either remove the Inhibition Suppression after reducing it to the amount you want or to use Option 4, which has no drawbacks except taking direct intervention by the player to do anything.
EDIT: Oh, there's also Option 5: Psychosism. The auras *can* technically reduce Inhibition, but it's random and unreliable. Don't choose that option.