Exit is like most festivals, you go there with friends to have a good time, good experience, if pick up comes, good, if not, no problem. I hear good things about Sziget, you also have lake balaton in Hungary, alot of people party there, i know many girls who go there. Cockfest is something you just have to accept with well known tourist destinations and festivals.
If you are in Serbia, best place to go in summer is still the splavs. Problem is you are stuck with locals, they have reputation to protect and for a solo foreigner it could prove a hard challenge. I am leaving Belgrade until 15 july, when i am back i have connections and can get you into places.
Best summer party spots in Europe are Croatian beachside : Dubrovnik, Hvar, Split. Most tourists here are from balkans but you get also many westerners. Quality is very high. Greek islands : Krit, Zakintos, Rodos. Most tourists here are middle class westerners, many Scandinavian girls from Sweden, Norvegia, Finland. Also many Russians. Montenegro : Budva. Mostly balkan and Russian tourists, very sexy girls, alot of mafia people here. Black sea coast Romania and Bulgaria : Varna, Sunny Beach, Constanta. Mostly Romanian and Bulgarian tourists, blue collar westerners. I also hear many good things about Odessa and Kyiv summer beaches.
This summer i am spending the entire month of august in Budva. I am renting a villa with pool there. Some girls from Belgrade are coming over and my friend from Moscow who works with models is also coming over with alot of his girls. If anybody is around or wants to party hard Serb style, let me know.