There is they are called plastering retarders/retardants, never used them so can't tell you first hand what if any adverse effect it may have on the finished product.
Best bet is if your new at the game is work on small areas at a time until you have mastered the craft.
I tend to find doing a two mix finish with the second coat nice and sloopy helps.
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!