What is the right technique for acquiring the "th" sounds? Are there any really proved useful exercises or tongue twisters which can help to get them?
I think after some training I've managed to pronounce both
th sounds (voiced and unvoiced) correctly. But the problem is, I can't pronounce a clear decent th sound after some characters, like t, s, z, d, in a sentence without a pause or a little contortion. The goal is to use it freely in speech, which I'm definitely not able to achieve right now. I tried various exercises, like tongue twisters or just repeating some hard for me collocations, but nothing seems to cause a great improvement (or at least any).
My native language is Russian if it could help.
A few examples (the hard places are emphasized as code):
s the best thing i
n the world.
d there are many..
P.S. I've found a related question about pronouncing "th" sounds, but the question was about children with English as the first language. My question is intended for a grown-up foreign learner.