Of these ways, which would be the best way to work my lower back?

All I have is a 20lb dumbbell. 

Should I just hang my legs off my bed and do hyperextensions? 

Good Mornings? 

Explosive good mornings (just slightly bent, with a pyometric jump - like a pogo jump)?

Or swings (like with a keytlebell)?

Also, do you think I should do them explosively, or with a time under tension method? Should I do it for as many as reps as possible?

Thanks in advance?