If you have dice showing a blank can you use manipulate turn your dice to another blank on the dice or even back to the same blank on that dice, then turn opponents dice?

No. You cannot "turn" a dice back to the same side it was on. So if a dice has only 1 blank and you roll it, you cannot Manipulate that dice. You have to have a dice with 2 blank sides, and can then turn it to the other blank side.

Cool that will work. Thanks.

I think you can turn a dice to the same side.

Happy to be proven wrong though

Rules Reference, page 21, Turn (die) section:

"When turning a die, it must turn to a different side. A player cannot turn a die to the same side it was on before turning it"

There you go. Thanks.

You're welcome