There are techniques to cutting away the casting sprues to free the often fragile 3D-printed parts that involve slight pressure, when cutting, away from the part you want to free, and using fine, sharp scissors or clippers. I have seen some of these tools offered online and probably promoted by other modelers who use this website. I have had mixed results (though mostly successes) with such techniques, but it does take a steady hand, good lighting, and the right tools. With smaller, finer parts I have found it best to free them in groups from the larger flat bases that hold these parts, using clippers afterward to free the individual pieces. Some 3D-printed parts are very brittle and others are somewhat flexible, which make for easier cutting; you can get considerable variety in different model kits.