Animal fundraising/volunteering this Summer... (London)

Hi everyone....this Summer I am giving up my holidays to go and help in animal sanctuaries and dog rescue centres abroad. My GoFundMe link is: Protected content if you do have a spare pound or two:) I am looking for advice for travel as I will be going by train, or coach where necessary. I will be travelling from Brno (Czech Republic) to Barlad (East of Romania) to Kresna (West of Bulgaria) on to Florina (Northern Greece) and from there to Prishtina (Kosovo) where I end my volunteering at the Bear Sanctuary. I then need to travel via Bosnia and Croatia, along the coast and then across via Switzerland, ending up at St Malo. Would anyone be able to advise regarding best/cheapest/fastest options? I was going to buy an Interrail pass, but was worried that their longest pass would not cover my travel requirements. Any help would be greatly appreciated.