My baby has acid reflux and has not been feeding well- he either cries at the breast or falls asleep. He is mostly feeding for less than 5min and feeding infrequently. As such, he end up drinking only the foremilk and I noticed his poo is now green. FTM, so maybe my question may sound silly, but can I express out the foremilk until the milk is noticeable less watery/more 'white' before letting him latch to increase the chances of him drinking the hindmilk?

I think one way you can do it is to pump out the milk. The foremilk helps to quenches your baby's thirst and with acid reflux, you also need to make sure that your baby doesn't drink too much at one go. So using a bottle to feed your baby may help. Bottle feeding will also help with the infrequent feeding as I can imagine how tired you will be to feed so frequently. You may choose to latch on still and do a mix between bottle and latching on to make sure your baby gets the necessary nutrients he needs and also bonding through breastfeeding. Let us know you decide?