i like to make sure that both the postworkout shake and the next meal have at least an equal fraction of the days total protein intake. for example at 240g per day into 6 meals is 40g per serving, so that would be at least 80g for the shake plus meal (assume this is for a 180 pound male, protein is 1.5g/lb).
if the session had a high workload, then the shake goes from 40g to 60g and the meal from 40g to 60-80g.
for two a day training, i would split the high end of the dose into two and would consider taking in half my intake through the shake and meals, so 30g shake times 2 plus 40g meal times 2 gives us 140g.
assuming you smack a protein blend before bed at around 40g, that leaves 2 meals at around 30g - i'm guessing breakfast and the one before workout number two.
if one or both of the two-a-day sessions are as hard and long as your one-a-day, then simply take in the full protein dose (and other food too) at each such instance.