I had the same question about losing powder in the excitement of the moment. When lurking on some of the traditional forums I read about paper cartridges. So what I did was make a measured charge of loose powder in rice (cigarette) paper. I used a 7/16 dowel rod for a template to form the empty case and then filled with loose powder. I have not had an opportunity to use this hunting yet but have done some range testing and it does not seem to change the accuracy of my load.
I also have some of Lane's tubes. I bought 75 and split them with my brother and nephew. After my first range session with them I regretted not buying more or at least giving any to my bro. I will buy more because they are very handy.