In Sink Soap Dispenser

My sister asked me this week...do you have an in-sink soap dispenser in your kitchen and I said YES and I wouldn't have one again.  I picked my sink.  It had the hole, the faucet I liked had the dispenser, so it was installed. 
Can someone clue me in on the best, neatest way to fill the dispenser??  I know that you don't climb under the sink and wrestle it out from that tiny space...yes I tried that once, too.  But the instructions tell me just to pull out the pump and dump the soap in.  BUT...the first couple of glugs make a plug and it just comes back out the top and I know it's not full.  I tried straw at the same time to let out the air bubble, but that didn't seem to help.  I wonder if I should thin down my soap to make it flow in there a little smoother...
Wow, the world has major problems and I can't get the soap dispenser full.
BUT when we come up with a better way, it will make us so much happier!!
Have a great windy day and pull in some firewood.  I think we will need it before this week is over.