Yes, I have started practicing slips. I have been flying rubber powered free flight and RC for over 30 years but I always flew at a large facility where it wasn't necessary to slip the plane in. I have been away from RC for about 10 years and so I am rusty and need to keep practicing to get enough coordination to slip the plane properly.
It is effective if you don't get too fast a descent rate. When there is a cross breeze it would be handy to crab the plane just enough to deal with the breeze. Lately I have been going to the park that is 2 minutes away at 5:15am cause there is no wind at all till about 9am.
I have been flying about 4-5 mornings a week shooting touch and goes for an hour or so.