I crimp and solder. After crimping I tag the open end with solder because the adhesive lined heat shrink doesn’t seal that part well. I also fold the wire to help fill the terminal. Some MC4 crimpers have a good small crimp opening that does really well on non insulated. I turn the jaws around so that the opening I’m using is closer to the hinge. I also like these terminals(Amazon)because they’re not copper but actually brass that’s harder and doesn’t mush under the nut,(also harder to crimp. I don’t use the pink shrink that’s on them.