I have, but in a very limited way. I wrote a grant that got me $500 for traveling to an arts conference, back when Arizona still did such things. I've helped businesses write grants that helped them get on government programs, or attract investors.
If you're serious about wanting to learn the art of grant writing, check out libraries for best practices and style manuals. DO NOT fall for online programs that promise you unending fountains of grant money if you buy their course or book. Community colleges sometimes teach grants classes.