When the Bengalese don't do their duty, almost invariably as the Pin-tailed Parrot Finch chicks fledge, the only option is to hand feed.

With Pin-tailed Parrot Finches, keep the fledglings being hand-fed with the Bengalese as sometimes they resume their fostering duties after a few days.

The syringe

A 5ml syringe is the most convenient.  
Drill the exit hole to at least 2.5mm, 3mm is better, to minimise clogging.  

Sand, file or scrape the inner ridge at the top of the barrel to stop the plunger coming right out.  (shown by the green line in the photograph),

You need the plunger out to fill the barrel with eggfood.   
To stop the rubber end coming off the plunger adhere it to the plastic plunger handle with silicon sealant.   
A teaspoon handle makes a good spatula.

The mix

Take a heaped teaspoon of your eggfood, remove large seeds and crush to minimise large lumps which will clog the syringe.   

Add more water to get a moist paste which is quite wet but when stirred doesn't run (click thumbnail above for a better idea).

Add a pinch of protein boost and probiotics.   

Mix with water until mix is quite sloppy.  Leave for 2 or 3 minutes as the water is absorbed.  

Keep this mix in the fridge.  
Don't use the same mix for more than a day.   
Fill the syringe with about 1ml per chick.  
Dip the part of the syringe containing eggfood in hot water to warm it for 5 minutes.

How much/ How often?

4ml is probably the daily maximum, 2ml the minimum.   This varies as the chicks age (less as they get older). 

Once they are self-feeding you might supplement with only 0.5ml per chick last thing at night until day 10 or even 12. 

Maximum is probably better for first two days, thereafter a slightly hungry chick is better as it will call to the Bengalese and will seek food from the dishes.

Watch the chicks - they will let you know. 
1 - 1.2ml is probably the maximum at any one time.   
Less than 0.5ml isn't worth doing.  

Judge your feeding from the chicks.  If they are active they are fine.  
If any close their eyes after you have stood still in the bird room for a minute or two then feed.

The evening feed is the most important. 

Try to get at least 1ml in, even if it takes two feeds close together so the chick lasts the night.

Be a bit ruthless in the morning once they are fledged for a few days, to encourage begging and self-feeding.

The more frequent the feeds the better but we have fed 1.2ml at 7.30am; 1ml at 4pm and 1.5ml at 8pm.   The chick was fine.

How

Chicks vary right from day one.  There are the beak clenchers, the chokers, the regurgitators, the fidgets and the blissful - let's get this ml in ASAP!

I open the beak with sideways pressure from the end of the syringe.  
My wife somehow opens the beak with her thumb.  

Once the syringe is in, the food needs to fall behind the lip at the back of the tongue.  
Don't depress the tongue as the flap at the back is used like a paddle to swallow the food.  

Try to have the syringe entering slightly from one side to keep an air hole open.

Don't keep filling if the mouth is full and food is oozing out the sides.   

Stop for a minute to let the food go down.  
Judge the speed from the chick.  
Judge if the chick shows distress.  

I've only ever choked one chick out of probably 30 or 40 being hand fed.  
But that's one too many