Assuming you have a chin bar, use a chair to support your feet- sort of a crude assisted chin, but it works, especially when you start adding weight. Also, pay real close attention to your negs- before HST, I couldn't do more than 3-4 pullups. Then, I started doing negs, and got up to 12-15 reps after about a month. You'll probably find that you can do more after your 5negs is the moral of the story! BTW, if you want to hammer your lats, do pullups, not chins- the latter involves your bis more than you might want.
Jake