OK. I know what you mean. It was soft Ł. Back in the days in 60's and + used this soft Ł. You can listen to Niemen or Fogg songs from that days. It was very popular to sing, read poems or act with this soft Ł. Sometimes you can still hear it from old people living in borderlands. So... people are aware of this sound and you don't have to use hard Ł. Just say it as you regularly say it and it will be perfectly fine. Closer to the east of Poland, more natural it sounds ;)