Ok so quite often I can not use fondant and get that smooth beautiful look. So i finish it in buttercream. However it is really difficult to keep all of the crumbs out of the finished product. So any advice. And how do i make it smooth?

That's why it's called crumb coatingfor people who can't ice one coat without crumbs. If you crumb coat, it doesn't matter if you get crumbs in the icingyou're final coat covers it up.

To ice without crumb coating, you put the icing on thick and push it around without ever letting your cake knife touch the cake. Don't lift your knife unless you've gone backwards over the existing icing. You don't want to spread it too thin, or play with the icing. It helps to start with a big batch of icingplenty more than what you need. If you start with a small, minimum batch that you're trying to stretch to finish the jobyou're more likely to get crumbs. Once the cake is completely covered, the excess icing is removed by scraping or combing it off. It's helpful to have a really good turntable so you can smooth it in a continual swipe. If you need to swipe more than once, make sure to wipe the extra icing off the knife, scraper, or comb before trying again.