Yeah, shoulder rest is essential. Made sure you keep your left-hand wrist straight or slightly curved out, as you should with guitar. If you raise your wrist to support the neck of the fiddle, then you'll not be able to move around properly. Practice holding the fiddle just with your head/neck, without holding it at all with your hands - that'll get you used to supporting it properly. I know the trad fiddlers will have kittens at this, but there's things they just can't do cos their technique hamstrings them, so ignore them! :-)

Bowing, you need to keep the bow at right angles to the strings. As you get to the tip of the bow, bend your right wrist away from you, then that compensates for the tendency of your arm to pull the bow back. Conversely, when you get to the nut (I think that's what it's called - the end you hold anyway! :-) then bend your wrist towards you - that compensates for your arm tending to push the bow round the other way. Best way to get this sorted is to enlist someone else to stand next to you and correct you when you pull the bow round. It's perfectly possible to keep the bow in the same place on the string but to be pulling it round at either end, so it's difficult to tell yourself.

It's quite difficult to describe this, so it's very handy to find someone to demonstrate the movements. Once you've sussed what you're supposed to be doing, you can practice it on your own.

Grab.