99 civic si

I am doing a major maintenance on the car: changing all fluids, belts, water pump, timing belt tensioner, valve adjustment. I am following the helms manual.

First, I put the cam gears at TDC. Then I removed all the belts and timing belt. I just finished bolting up the new oem water pump. Now, I am trying to install the new oem timing belt.

I first put the new timing belt starting at the crankshaft-->timing belt tensioner (adjusting pulley)--> water pump--> intake camshaft--> exhaust camshaft. My friend took over at the intake. I loosened the timing belt tensioner bolt to lessen tension of belt. When the timing belt was placed on exhaust side, the exhaust cam gear slightly moved about 2-5 degrees to the left/counterclockwise (Teeth are no longer aligned) and cam gears are obviously not at TDC anymore.

Well, it looks to me the cam gears are slightly uneven (still close to TDC). It seems the exhaust cam gear slightly moved and intake side is still in correct position for TDC.

How do I set/line up the cam gears equal and back at TDC so I can place the timing belt correctly with the right timing?

Also how do I prevent this from happening again and properly put the timing belt on?