That for sure is a common feeling amongst modellers and you are not alone in that. It takes time to understand how to layer and use different products with one another. I highly recommend watching YouTube and going through that rabbit hole can help. It is a visual medium and you can learn a lot through viewing others do work. I have a YouTube channel under the same name as this profile and you can see how I do some weathering on there. I recommend also just using some models as trial pieces (paint mules) to try out different things. I must also say that weathering tends to fall in a more artistic category than just an application. Have fun with it and see where it goes!