Randomizing wound allocations from exploding transport

Transport explodes, 5 guys inside need to take wounds. Opponent rolls 5 dice and wounds 3 models.

I resolve these as for shooting hits (pg:80). I cannot tell who is closest so I turn to pg:15, and it tells me to randomly determine which model is closest. I turn to pg:5 and under Randomising I must assign a number to each model.

I assign 1, 2, 3 and 4 to normal guys and assign 5 to the special weapon. I then roll 3 dice (number of wounds) to find who takes the wounds (D6 result = the model's assigned number).

I then roll the saves on those assigned models and remove casualties.

Am I doing this right???

And if its a unit of 10, split in half, D6 for which half, then apply the same number system to the half?

EDIT: Or is it simply the controlling player allocates the wounds..which is what I've been doin up until now

Don't worry you don't have to deal with randomisation. Controlling player (the person who owns the transport) allocates the wounds it says so clearly in the rule book.