In my experience every mold has it's own personality. I have considered putting the "directions" for shooting a particular mold on the mold itself (laminating first) but I haven't done it yet. I have molds that are very forgiving and others that require me to hold the pressure for 20 seconds etc. Some molds are just fickle. I had to cut vents in my Croaker molds from Do-It to get complete feet. I have a craw mold that will get dents in the claws unless I shoot it fast and hold pressure for dang near 30 seconds. As discussed previously, plastic temp. is also an important factor. Some of my molds shoot better cooler and others are almost impossible to shoot cool (310-320 degrees is what I consider cool).
Oh, and if you change any variables along the way like plastic type, increasing the amount of glitter etc., the whole learning curve starts again!
Not trying to scare you off. Just enjoy the ride!