Just wanted to make sure I do this in a good way.

What method / application do you use for Timestretching?
Also, what method / application to get rid of the artifacts created by Timestretching

I work in Cubase 8.

Thanks a lot!

It sounds like you’d benefit from spending some time with the manual in front of you and by trying out each algorithm on various types of material as they’re all designed for different uses.
Plenty of videos online explaining ‘how to’ if you try using one of the myriad search engines available too…