OMG - Swans, what are you trying to do to this guy. Learn waht your talking about before giving advice.
Proteinboy - dont do it 5-6times a day or your muscle will not heal. Stick with your 4 reps, the only way you can get better is to get stronger, so do 25-30 reps, over as many sets as neccesary, even if you end up doing 1-2at a time. push thru the pain barier, its easy to stop and giv up with chinups, but you gotta learn to skweez!!! learn to control your lats.
dont train them again untill they stop hurtting. if they hurts then they have not healed and you'll only damage yourself.
remember to chage from wide grip and close grip.
Wide grip with hands forward is hardest so get it out the way 1st.
close grip with hands facing you is easyer so do it last.
train your lats just like any other muscle, The only "trick" to get big lats is knowing that you can only get them big with hard work.