I insulated my own house despite not being particularly skilled (to say the least) and absolutely loathing DIY.
A bit more context. I live in a house that was built in the early 70s. When I bought it back in 2009, there was hardly any insulation and due to the way it was built it was draughty and cold. A few years ago, I had the walls insulated, which made the major rooms a bit warmer. However, the house was still cold, part of the problem being the crawlspace and concrete floor. Last year, I got all the debris out of my crawlspace and put a thick plastic film on the sandy floor. That had instant effects: not only did the humidity drop (and some occasional musty smells), but we also needed to use less natural gas to heat the house. This year, I finished that project by insulating the bottom of the concrete floor with thick rock wool. That job took me several weeks. First, i had to glue wooden slats to the bottom of the floor and then I had to apply the rock wool.
My DIY skills are poor. I did this alone. It was a hell of a job which I do not intend to do a second time. However, the rewards, both in terms of comfort and savings are great.