You will get lines when you lay it on. When you have layed it on, let it pull in a bit, then go over the lines.
This 'might' leave more smaller lines but thats ok.
Get your second coat on. You will have lines again.
Let it pull in and take the lines out again.
Now as the plaster pulls in, you keep taking the lines out. As in, 10 minutes, take the lines out. 10 minutes later, take lines out. etc...
You will end up with a fairly line free wall

Now polish it.
It takes time to get the knack mate. keep at it. Learn how the muck works on different surfaces and observe the different times it take to pull in on different surfaces.
Its not the kinda job you can just get going at. It takes practice and a low pay for a couple of years! ;D