If you like this technique @user_not_found you might like one of my play tricks, get a sheet of clear acrylic (sometimes this is called perspex or plastiglass) and cut a 1cm hole in the centre. During your long exposure have the sheet in front of the camera and while keeping the hole over your main subject rotate the plastic. This will give you some really interesting flare and light trail effects. You can make this even more interesting by scratching the sheet or placing gel on it. Good luck with your experimenting and have fun.
Regards Paul