This repo is for NC2 on SM-N900A. Various ports exist - check your phone's xda forum.
Modify the options in app/src/main/java/com/benwaffle/nc2flasher/MainActivity.java.
Place desired kernel .img in app/src/main/assets/.
Compile with ./gradlew assembleRelease, the output will be ./app/build/outputs/apk/app-release-unsigned.apk.
All this does is run dd if=kernel.img of=/dev/block/platform/msm_sdcc.1/by-name/boot