Once you have all the material ready it will not take more than 30 min. to make this feeder. I am going to add a 25Lt container above the existing bottle in order to increase the capacity. The 25 Lt container will feed into the existing 5 Lt bottle. This arrangement should give me at least a week if we have to go away. I could not find a bigger bottle with the same diameter outlet and tapered shoulders to fit into the down pipe.
This method should work for ducks as well. You might just have to widen the gap at the bottom because I am not sure if they will be able to get the food out from underneath the pipe. Do not make the gap too big because then the food will spill into the gutter and you will have wastage again.
As far as the type of food is concern the following. I start my chickens off on Starter mash up until a 6-8 weeks. They do get the odd cup of mixed grain for scratch as a treat. From 8 weeks they go over to pellets - no arguments- no discussion. They still get their scratch and scraps from the kitchen. They have the free run of our very big garden for at least 3 hours every day. Unfortunately we have to guard them whilst they are out because of predators.