Bonus Damage Aura - Dumb question

HOw do I do a bonus Damage Aura.. which ability/buff do I use

so the unit attack damage would be 5 +3 damage (bonus) and is it possible only to give this bonus to Mechanical types only.

Ok I think I got it.. since the bonus is applied to the turrets only I edited the trueshot aura. which deals a percentage which is good enough for me


If this is the way to do it dont reply.. If you have a better way let me know

"Command Aura" provides an absolute damage bonus. It's a neutral spell.

As does trueshot, I believe, if you check the box refering to set or percentage values.