The problem with many electronic tuners is that you have to be sort of in the ball park before they are really useful. And few of them are designed specifically for bass. The Korg GA-30 is an inexpensive one that also emits real sound tones as well as has a reading screen. It has a button that toggles between bass and guitar settings, but even it will give some false info if you are way off from the target. If you use the auditory setting to tune a bass you will be tuning to a pitch an octave above so you would need to be able to hear that and perhaps use the 1/2 string harmonic instead of the open string fundamental. If you can get to an 88 key piano, I have found this to be the best auditory reference, because the strings in a piano are long and fat like those on a bass and the overtones are more similar. Even a good electric piano set on one of the acoustic piano settings works well as long as it has 88 keys. The corresponding notes are white keys and they are the 12th white key (from the lowest note up) for the E string, the 15th for the A, 18th for the D, and 21st for the G. If your bass guitar is in tune, Doug Ring's method will also get you close.
That being said, it is great to be able to tune by ear when conditions allow it. The best way to learn to do that is with someone showing you who already knows how.
As far as the bowing thing goes, you need rosin, yes, but mostly you need a good teacher. There are two different types of bows for doublebass, french and german. One will be better for you than the other, but you need a teacher to learn to use either one of them correctly. I played bass guitar for more than 25 years before I got my first DB. I realized really quickly that I needed a teacher. There was just too much new information to digest alone. Chances are if you proceed on your own for very long you will develop some bad habits, make deleterious changes to your instrument, or even worse, hurt yourself.
We can help you some on a forum like this, but this instrument should be sold with at least one warning: "Teacher necessary, but not included". The better places that sell them usually do offer lessons as well. Good luck and congratulations on your move to the DB. With patience and perseverence you will reap the rewards it offers.
