This my method for playing Electric Uncle Sam. 
I believe this is the correct of playing it.
It is a pretty basic song. Not too much skill required.
This is for a 4-string.

s=slap
p=pluck
*=slap with hand

(Intro)
   s s s  s s s  s s s  s s s  s s s  s s s  s s s  s s s
G----------------------------------------------------------|
D--7-6-5--7-6-5--7-6-5--7-6-5--7-6-5--7-6-5--7-6-5--7-6-5--|
A----------------------------------------------------------|
E----------------------------------------------------------|

   s s s  s s s  s s s  s s s  s s s  s s s  s s s  s s s
G----------------------------------------------------------|
D--7-6-5--7-6-5--7-6-5--7-6-5--7-6-5--7-6-5--7-6-5--7-6-5--|
A----------------------------------------------------------|
E----------------------------------------------------------|

   s   s  s s * * * * * s   s  s s * * * * *
G-------------x-x-x-x-x------------x-x-x-x-x-|
D-------------x-x-x-x-x------------x-x-x-x-x-|  x4
A-------------x-x-x-x-x------------x-x-x-x-x-|
E--0h2-2--0-2-x-x-x-x-x-0h2-2--0-2-x-x-x-x-x-|

   s  s s p p s s s s s s s s  s s    s s p p s s s s
G---------x-x-----------------------------0-0----------|
D---------------------7-6-5-------------------0-2------|  x4
A-------------------------------------------------0-2--|
E--2--0-2-----0-2-0-2-------2--0-2----0-0--------------|

   s   s  s s * * * * * s   s  s s * * * * *
G-------------x-x-x-x-x------------x-x-x-x-x-|
D-------------x-x-x-x-x------------x-x-x-x-x-|  x4
A-------------x-x-x-x-x------------x-x-x-x-x-|
E--0h2-2--0-2-x-x-x-x-x-0h2-2--0-2-x-x-x-x-x-|

   s  s s p p s s s s   s  s s p p s s s s   s  s s p p s s s s   s  s s p p s s s s
G---------x-x------------------x-x------------------x-x------------------x-x----------|
D-------------------------------------------------------------------------------------|
A-------------------------------------------------------------------------------------|
E--2--0-2-----0-2-0-2---2--0-2-----0-2-0-2---2--0-2-----0-2-0-2---2--0-2-----0-2-0-2--|

   s  s s p p s s s s s s s s  s s    s s p p s s s s
G---------x-x-----------------------------0-0----------|
D---------------------7-6-5-------------------0-2------|  x2
A-------------------------------------------------0-2--|
E--2--0-2-----0-2-0-2-------2--0-2----0-0--------------|

   s   s  s s * * * * * s   s  s s * * * * *
G-------------x-x-x-x-x------------x-x-x-x-x-|
D-------------x-x-x-x-x------------x-x-x-x-x-|  x4
A-------------x-x-x-x-x------------x-x-x-x-x-|
E--0h2-2--0-2-x-x-x-x-x-0h2-2--0-2-x-x-x-x-x-|

Rest until it start again with the two plucks.

     p p
G--|-2-2-|---------2-2-|
D--|-----|-------------| Repeat until the song ends.
A--|-----|-------------|
E--|-----|-0-2-0-2-----|

Enjoy guys. This is Electric Uncle Sam. Listen to the song to get the timing just right.
Which I am sure you guys will do. This song is not hard to learn.