I don't know which trains you can book in Dublin. Maybe ask them first via phone.

If you let us know which train(s) you are trying to book (route, date, departure time), then it is possible to give advice on where best to book.

HI 

I am traveling from prague to krakow on 10/7/22

krakow to budapest on 13/7/22

budapest to solivenia 16/7/22

Prague to Krakow: book via Czech railways. Look for the journey and then click on "I want a reservation only”.

Krakow to Budapest: book at a ticket office that can do international reservations, e.g. when you're in Prague. Also possible in Germany, Austria and other countries.

Budapest to Slovenia: reservations are optional for international travel (day train). For the 8:40 departure, there will be a partial bus replacement in Hungary, between Veszprém and Ajka (normally 30 min. by train, now 40 minutes by bus). Timetable has been updated on the Hungarian railways website.

All these are best done locally at THAT station. In fact the DAYtime trains on these routes are only optional REServ=not mandatory, but overnight not. I do not think that CIE/IR is since many yrs even able to contact other railways for such mundane matters. best way is-in the past anyone could think of that all by themselves: on arrival just do not rush out of station-spend a few more mins, find counter, see how it works, have it done there&then-I assume you stay a few days and want to see town.

And in general-to quell these enormous fears-works just like on IR-train: are not fully booked weeks ahead.

thanks for your reply , if i leave it until i get to the stations will the trains not be booked out ?

Trains in Poland are reservation compulsory (both Daytrains and Nighttrains). 
So please don´t share false info.

If I wait until I fly to Prague and then go to the railway line to book my trains is it possible to book the following there :

prague to krakow 12/7/22 

krakow to Budapest 15/7/22

budapest to Slovenia 18/7/22 

can I book all of my seat reservations at Prague station ?

Yes you can. But you can already book the first one online (see my previous post). The second one should be fine a few days in advance, at least for the day train. The third one (I assumed you mean to Ljubljana) I wouldn't bother to book: it's optional and there will be fewer people anyway because of the rail replacement bus in the middle.

Thank you very much for your reply it’s a great help , I think I will try book all 3 online as I am worried they will be sold out 

@seewulf May I ask what’s the source for this? PKPs own interrail reservation guide states as follows: EIP mandatory, EIC optional, IC optional, TLK optional, domestic night train mandatory for sleeper / couchette and optional for seats, EN mandatory (as of end of COVID restrictions - all trains have been mandatory during COVID restrictions). 

It’s always possible that I didn’t get or lost any newer information (but that’s the most up to date I got) - but otherwise I’d thought that mcadv is indeed right for at least most of the trains?

Kind regards, Hektor.

We’re going around in circles. Only the first one is currently possible online. The last one is unlikely to sell out.