These are both in the Power-Manipulation category (see page 16 of the Mentalism Companion). They have a Combined progression, same as other skills in that category.
Personally, I would not use these skills, which are optional. The net effect is that the spells of pure mentalism casters will be harder to resist than any other spells in the game, semi mentalism casters might get a small bonus (but don't really have the DP to spend on it), and mentalism realm casters will be much more resistant to the subtype m spells of other realms. I don't think that's a good shift in the power level of the realms unless you want a game that really focuses on mentalism and makes the other realms less important.
The use of Mental Control (Assault) is:
* Caster casts a mental spell (subtype m)
* Caster makes a static maneuver with their full bonus for Mental Control (Assault)
* Caster makes a BAR roll. If the static maneuver was successful, they add their number of ranks in Mental Control (Asssault) to the BAR roll.
* Target makes a RR
The use of Mental Control (Defense) simply adds the skill bonus to the character's RR vs mental spells.
