Rather than use books or worksheets or pencil grips I'd suggest a pen or pencil that encourages correct grip - yorpen or penagain (lots of similar on the market) and lined paper and teach correct formation starting and finishing points and sequence of movements.
It's very easy with books and worksheets to produce something that looks right but is really establishing more bad habits.
It's helpful if he says how he is forming the letters as he does it keeping the same "speech"
Curly caterpillar family
Anticlockwise movements
c round
o round, round and join
a round, up, down and flick
d round, up, up, down, down and flick
g round, up, down, down and round
q round, up, down, down and tick
s round and round the other way
f round, down, down and round ? across
e across and round
one armed robot family
down, up and over movements
r down, up and over a bit
n down, up, over, down and flick
m down, up, over and down, up, over, down and flick
h down, down, up a bit, over, down and flick
b down, down, up a bit, over and round
p down, down, up, up, over and round
k down, down, up a bit, over, round, out and flick
long ladder family
mainly down and round movements
l down, down and flick
i down and flick ? dot
t down and flick ? across
j down, down and round ? dot
u down, round, up, down and flick
y down, round, up, down, down and round
zig zag monster
diagonal movements
v down, up
w down, up, down, up
x down, stop ? down, stop
z across, down, across