Slightly lewd/crude joke one might find amusing if told correctly

Good morrow galant chaps, the joke we refer to is as follows: you say to the chaps at the foxhunt kennels, I say then, what's the difference between a Japanese fellow and a Chinese fellow?

Then your riding mates say, we jolly well don't know, tell us then old boy!

Then, to 'pull off' the punchline, you say: the Japs look like they're struggling with constipation mightily, and you pull a grimacing kamikaze styled sumo grimace face as if struggling to pass stool, and then say, whilst the Chinese fellows appear to be constantly jerking off and you jolly well make like you're jerking off with a good squinting look on your face as if ejaculating as it were.

Good o then, happy trails

https://youtu.be/wr7mP77_S9k