orphaned kittens

I have read the orphaned kitten FAQ but still have a few questions.

We have 4 3-week old kittens. We found them in a junk car when we went to
tow it to the junk yard yesterday. Three of them are sucking the bottle but
the smallest one just hasn't gotten the concept yet. I have managed to get
some food into her. How long should I give her before trying another method
of feeding?

I have gotten all of them to pee but none have pooped yet. How often should
they do that? How long do you need to wipe their bum before they usually do?

Is there a good way to start getting them interested in drinking/eating from
a dish?

Wendy