I just use one of those dental irrigators (large syringe with a plastic tip) to fill the bowls through the vent tubes. You can get them from your dentist for free if you ask. Just be sure to clean up the gas after so it does not get eaten up. Been using the same one for years....
$8 for 2 of them at amazon.com
http://www.amazon.com/Watts-Syringe-...uct/B002OXEURA