Use "all of" ONLY before pronouns like "us," "them," or "it." BUT use just "all" if it precedes a noun.
Conducted training with all of the new personnel in the region. D (incorrect)
Conducted training with all new personnel in the region. C (correct - personnel is a noun)
FOR MORE GRAMMAR TIPS SEE:
1. Grammar Monster - http://www.grammar-monster.com/index.html OR
2. Grammar Girl - http://grammar.quickanddirtytips.com/