Encryption Help

im going to be traveling soon so i want to have my stuff safe. i want to encrypt some files that stay on my portable external hard drive. is this possible by using disk ultility like i do to encrypt things on my internal hard drive. whats the best way to do it? easiest and safest? i just need it to be safe and ask for a password so noone but me can enter or see it. remember its going to be on a external and encrypter. so whats the best way and how
thanks and is it safe to encrypt alot. like about 50-75 gbs

You can make an encrypted disk image with Disk Utility and save it on an external drive. If you make it as sparse image, it will only take as much space as the size of the files in the image.

Otherwise, you could use TrueCrypt.