Yes, Polish /r/ is identical to the Irish one, but we don’t have anything like Irish sleder r . Old Polish had a sound-like-that, but it evolved into modern ⟨rz⟩ which is just [ʒ ~ ʐ] (Czech still has ⟨ř⟩ [r̝] which is something between slender r and the zh sound).

And most of our slender (or soft as we call them) consonants have a bit different realization (are even more palatal), some of the Czech and Russian sounds are closer. ;-)

But still, I agree, that Irish phonology is easier to a Pole (or any other Slav) than to an English speaker. English has a shitload of phonemic vowels, and very few consonants, while both Irish and Slavic languages differentiate just a couple vowels, while having this a-few-variants-of-each-consonant thing.

Kto wiedział? Brzmicie bardziej irlandzcy niż Irlandczycy sami.

Bríd's work on forvo is the most incredible resource for Irish learners like us. I cannot say enough how thankful I am for her work and any time it comes up I am glad to repeat it

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ЯГОН ТОҶИК НЕСТ ИНҶО???

Dia is Muire dhuit!

As people have already commented, pronouncing any r's in Irish like the English r ([ɹ̠] or [ɻ] usually) is incorrect Irish. I don't think that a single dialect traditionally has or had this sound. (C'est tout aussi incorrecte que de prononcer le r à l'anglaise en français.)

Typically Irish has two r sounds:
- a broad r [ɾˠ], which is a velarised tap or flap, almost identical to the Spanish r in pero.

- and a slender r [ɾʲ], which is a palatap tap or flap (there is some slight variation of this sound depending on the dialect or position in the word).

If you're interested in more details there is also a devoiced version depending on the position in the word, and a trilled r, like in the Spanish rr in perro, which is noted in a few sources to still have been in use by some speakers in some dialects. I personally like to maintain this distinction but it's not necessary as most native speakers today lost that sound.

I find it interesting that you say 'almost identical' because it ties in with something I have wondered about in the past.

Spanish 'pero' has a (plain) alveolar tap i.e. [ɾ].
Irish broad r is a velarised alveolar tap i.e. [ɾˠ].
Irish slender r is a palatalised alveolar tap i.e [ɾʲ] (at least in the default realisation of slender r).

So you might expect that the Spanish tapped r, having no secondary articulation, would be midway between Irish broad r and Irish slender r. But in practice, that is not the case. Spanish tapped r is far closer to Irish broad r than to Irish slender r. In fact, I personally can't hear a difference between Spanish tapped r and Irish broad r; and you will occasionally come across people who say that they are in fact the same. This is despite my understanding that a velarised consonant should sound deeper than its plain counterpart.

For instance, you might theoretically expect the difference between [ɾ] and [ɾˠ] to be the same as the difference in English between light l [l] (which is a plain consonant i.e. it has no secondary articulation) and dark l [lˠ] (which is velarised, thus giving it a deeper quality).