I like to wash even new tanks with a paste of salt with just enough water to all you to scrub with it. Then a simple rinse with water.
If you haven't water tested the tank - even some new ones leak - fill it about half way and wait an hour or so. If all is ok, fill just to where the rim blocks the glass. That's high enough for now. Cycle the tank and all should be fine.
Until you have it cycled, 70+ will be fine. It will give you time to slowly bring it up, and save you some small cash and water until the cycle is complete.