Guys, I found a solution myself.
You should have a file named portal -ext.properties in
$ TOMCAT_DIR / WebApps / ROOT / WEB-INFO / classes
Or, more specifically, for my setup win C: \ Liferay \ WebApps \ ROOT \ WEB-INF \ classes
The file will store the value
theme.css.fast.load = false
This will not allow liferay to look for all_packed.css, and therefore you can change your material without recovery and CTRL-R to refresh the page and see the changes.
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