I'm the same mate. I had to move the wifes Cobalt blue the other day and the bloody thing did a runner. I proper filled my pants.
We use a larg pop bottle. Cut the top off so you have a large funnel. Our is about 8" long from the top. Leave the cap on. Gently place the bottle over the t at a slight angle and using a paintbrush coax the t inside. They tend to go in forwards but not turn around. If you have a fiesty one you could always use some thick card to 'seal' the bottom.
Thats how we do it anyway. Pant filling sessions are plentiful in this house...lol