The way I do it is this:
Add up all the shares. In this case, 4 shares from the full-shares belonging to players, and 2 shares from the 4 halves from the companions. This means 6 shares.
Then, divide the total by 6. This gives you the value of a full share (i.e. the amount each PC gets) and halving that amount for each companion.
800/6 = 133 (with a coin left over)
133/2 = 66 (with a coin left over)
So, each PC walks away with with 133, each companion 66, and there's a few spare coins which I usually handwave away as getting lost behind the back of the sofa or whatever.