A few possibilities.
First off this is a good product, I went through a gallon of it, everyone's car I put it on liked it.
Smears/streaks can be caused by a few things.
1) Not shaking the bottle really well initially. A few shakes afterwards per section done also helps.
2) Loading up the wet towel with product. In the application video for the wet method, 2 towels are used. I used 3. Two wet and one dry. Swap out wet towels after each section, this ensures an even application every time. Stick the used one back in the bucket under the fresh one, repeat each section done.
3) Not enough water on the car. HGG is a water activated acrylic resin. It needs water to activate. After washing, if the water is drying too fast, fill a spray bottle with water, distilled works best, and mist each panel before spraying HGG on.
4) Using too much product. A little of this goes a long way. Use less product. Streaks are basically unactivated product, so if you see them, after using the dry towel, wipe slowly with fresh wet towel to activate product. No pressure is needed, then wipe with dry towel. A 16 oz bottle should do around 11 applications to a G5 Camaro.
A plush microfiber works really well. I used RC Everest 1100's, but any plush towel will do.