Do yourself an additional favor and don't use less - it nowhere near as powerful as alternatives. go with sass or stylus and I absolutely promise you it will pay off. gem install sass then run sass --watch /path/to/sass_file.sass and you're good to go.

Just setup LESS when you start the project. Though if you are having a hard time using it that means you aren't getting much value from it. Using more, better mixins will make a huge difference. Checkout Bootstrap's mixins.less file for a starting point.

SCSS, being a superset of CSS, is an easier transition. If its valid CSS, it's valid SCSS, so you can upgrade incrementally. LESS is totally out for me, since it sometimes chokes on obscure, but valid CSS declarations (e.g. some browser prefixes and hacks).