I've done it in the past by filling a soft drink bottle up. Blow the balloon up and pop the end over the bottle and then pour in. Good luck with tying it up though. It's pretty tricky.
MessyDarla probably has some good advice for you, she streams every friday and you could always ask then and possibly even get a demonstration/walkthrough
This is the question that stopped me lurking on this site nearly 22 years ago. No one knew how back then so I signed up and chipped in with 'fill a bottle and inflate balloon' technique. It works perfectly a balloon takes about 4 litres, but that's a lot of mess (I know from experience when I did this on a bed). It's a great splosh method...anyway, personal favourite was a surprise;
Warm custard and then 2 cans of whipped cream put in a t-shirt tucked into underwear. I decided to do it in the shower and hosed myself down in warm water before popping the balloon. The wet t-shirt was tight so snapped against my body, it felt like I had been pied in the chest and the custard was forced into my underwear at high speed!
If you use a 1 litre water bottle, with the sports cap you can squeeze the messy substance into the balloon quite easily.
Pre inflate the balloon, squeeze and twist off the opening and then feed this over the bottle top. untwist the balloon, invert the bottle and swap the mess for the air.
Using this method it is possible to twist the opening closed, separate the two, refill the bottle and repeat.
Once you have the knack it's fairly easy.
I've also used a larger bottle with a sports cap from a water bottle.
Love you, too
