It takes a lot of effort, and even more time. I’m really tempted to buy an electric sander to make my life easier.
(By the way, that’s not my hand, but it is the same sanding block I use)
I’m not against power tools, but they tend to create a lot more dust and noise than hand tools. This means that my ability to use them is even more limited; can’t use them at night, and I really need to empty my workspace of bathroom gear before starting work.
Although, the idea of making sanding easier is driving me to research power sanders: