Struggling to differentiate between the 'll' sound and 'ch'—any tips for my recordings?

I’m obsessed with getting my Welsh pronunciation right, so I’ve been recording myself reading S4C transcripts daily. Even after weeks of practice, my ear still can't quite tell if I'm hitting the lateral fricative correctly compared to the voiceless uvular fricative. Are there specific tongue placement exercises for these two sounds that actually made a difference for you?