I have done a fair amount of looking into these websites, and in my travels, I have only met 2 people who have managed to hitch a boat trans atlantic.
one used a website his first time, and has goe round trip from europe to the carribean 2 times now. the other just found a ride asking around in the canary islands. I think that its not unreasonable, and both people have told me that it ended up being quite easy, and assured me that if I really want to catch this ride, I will certainly find it.
Good luck to you, do a bit of research, and maybe start with a shorter trip. a month is pretty average for crossing the atlantic, and if you get sea sick, you will have a shitty time, and the person taking you probably wont appreciate it much. Your window for this year is over, but next winter between the end of october through february, get your ass to the carribean and find a boat!
I will be making this trip next winter, since I missed the majority of the traffic this year.
Good luck in your travels-