I just started the learning curve on some 3D Solutech Clear PETG. I know I will never get a truly transparent print, even with 100% infil, but my first attempt is very frosted internally from the default S3D "fast honeycomb" infil pattern. I'm trying a rectilinear pattern now, and it doesn't look much better.
One thing I noticed is that the perimeters look pretty good. They aren't exactly clear, but they aren't nearly as frosted as the infil material. I can increase the number of perimeter passes to take advantage of that. I will check in a preview, but I'm not sure what happens if I pick (for example) 6 perimeter passes, but there is a thin section of the model that is only 8 passes wide. Hopefully it is smart enough to dance around that...
One other thing I've learned is that if you've run red filament on your last job, no matter how clean you think you've got it, the first print comes out slightly pink... I used a foot or more of eSun's cleaning filament, but I guess that wasn't enough.
Any ideas or suggestions would be appreciated.