Meditation often happens naturally when people pray. In Judaism, prayer, when performed with complete devotion is a form of meditation. Submit yourself to the thoughts and feelings that come up during prayer without judgement and turn to the positive thoughts of love and acceptance, that is the process and we often forget that we do this while meditating.
The first five positive mitzvot and the first negative mitzvah are fulfilled only through meditation: I am G‑d your G‑d who took you out of the land of Egypt to be your Gd. Knowing that there is no power other than G‑d. You shall have no other gods …
During tefillah, you must focus your heart on the meaning of the words your lips are uttering. You must imagine G‑d’s presence right there before you. Dismiss whatever thoughts are bothering you until you are left with a clear mind to focus on your tefillah…
This was the practice of inspired and legendary people; they would seclude themselves and focus on their tefillah to the point that they transcended their physical senses, and their mental powers dominated bringing them close to prophecy.
If an extraneous thought comes into your mind during the tefillah, stay quiet until the thought disappears.
It’s necessary to think about matters that subdue the heart and focus it on your Father in heaven. Don’t think about empty matters.
This is a very helpful article that may encourage you to open up to the process of religious meditation. As for the question posed in the title, of course meditation techniques are Kosher, in fact it is a natural part of praying and brings the same good feelings of calm and peacefulness as it does for non religious meditation.