I used paper tape on my ceiling joints and it bubbled in a number of places. What is the cause and what is the remedy? Thanks

Hi, I am new to these forums and read back a ways but could not find a similar project so maybe one of you can help me. I started a home remodling project where I removed a couple small interior walls (not load bearing) between a closet and crawl space in order to make a small 10x10 room for the kids to watch TV and so forth. Now that the old walls are removed, new ones built and electrical in and working, I am at the drywall phase. My question is, in the area where I removed the old walls there is the 5 inch width area from floor to ceiling (and across the ceiling) where the wall used to meet that I need to put drywall in. Can I just cut long 5 inch drywall strips and screw/mud/tape or do I have to rip out more drywall and put in larger sheets. There are studs and boards where I need to screw so that is not a problem. Any advice would be appriciated. I can also give more information if needed. Thanks!