Without all details impossible to tell. There are probably many other ways to avoid this sending by post. And most likely you worry way too much about it as you say MAV/HU trains.
But begin with simply reading the informative page about how to make reservations and perhaps you will find that several of your plans simply cannot even be made online.
Please give details of the train(s) you want to book (origin, destination, date, departure time) so people can suggest alternative ways of booking.
So the trains we need booking for is:
Budapest (Nyugati) - Bratislava Hlavna Stanica
Bratislava Hlavna Stanica - Prague Hlavni Nadrazi
Venezia Mestre - Como S.Giovanni
Como S. Giovanni - Cannes
Thank you
Please add dates and departure times.
30th of may 11:40-14:03
Budapest Nyugati - Bratislava Hlavna Stanica
31st of may 12:06-16:42
Bratislava Hlavna Stanica - Prague Hlavni Nadrazi
12th of june 14.48-16:47
Peschiera Del Garda - Como S.Giovanni
13th of june 14:10-21:08 (change trains in Milano at 15:10)
Como S.Giovanni - Cannes
30th of may 11:40-14:03
Budapest Nyugati - Bratislava Hlavna Stanica
Reservation is optional and can be done via Czech railways for CZK 75 (~3€). Look for your journey and click on "I want a reservation only”, and then add the other passengers.
Or for 2€ via Slovak railways. Look for your journey, click on the shopping cart and then on "I want to purchase only reservation”, then on Reservation. Add all passengers (with no discount) and then click Continue. The website is a bit slow bit it gets there.
31st of may 12:06-16:42
Bratislava Hlavna Stanica - Prague Hlavni Nadrazi
Same as above. (Czech or Slovak railways)
12th of june 14.48-16:47
Peschiera Del Garda - Como S.Giovanni
Book via ÖBB using these steps. Price is 10€ per person.
13th of june 14:10-21:08 (change trains in Milano at 15:10)
Como S.Giovanni - Cannes
This journey does not exist, at least not with these times. Please check the timetables.
It looks like the 15:10 train Milan - Ventimiglia does not run after 10 June.
