Mouse club! >:O
I used a mouse from 2008-2015. An old 2003 Dynex corded laser. This is one of the last pictures I drew before it finally died. RIP. I got a tablet shortly after.
You can get good at using any drawing tool, even if it is a brick. I often hear young artists say "if only I could get a tablet" but in the meantime you can still draw with a brick and get good at using it just as well.
I draw on Paint.NET sometimes but it always feels very clunky compared to other drawing programs. I think it's meant more for editing, which is what I use it for.