newbie, we’re glad to help! This stuff is not something people just know how to do right off the bat, we all have to learn and be taught. To your question of “success,” I would consider someone to have “mastered” a certain size if they can insert and remove it comfortably and without pain. HOWEVER, something I didn’t know at first was that you rarely feel this way until you’re able to work your way up to the NEXT size. By this I mean that you might be working with one size that you’re pretty comfortable with, you only have a small amount of discomfort using it, so you move up to the next-largest size and then suddenly that SMALLER size doesn’t give you any trouble at all. This is how a lot of people move through the dilators, so it sounds like you’re still getting used to the 4th size, but I bet the 2nd size feels like hardly anything at all to you. That just means you have more work to do with the 4th one and will make progress as you’re able. I hope that helps but let me know if you have other questions or I didn’t explain that well!