Playing Tips -

In my opinion, there's really only one really good playing tip -
and that's to do what feels right for you. If it sounds good, it is good.
A good case in point is the classic question - "what finger should I wear the bottleneck on?"
Well, there are pros and cons.I used to wear the bottleneck on my middle finger.
I got quite far with this position, even though it did tend to look awkward sometimes when I fingered chords.
I got a good tone, though, and I could do some things that pinky-wearing sliders had a hard time doing.
I wrote songs that i wouldn't have written if I'd worn the bottleneck on my pinky.
Then i met Steve James, and that was all over.
I couldn't physically play - even begin to learn -
Steve's stuff if I didn't switch over to my pinky. I did, and now that feels like home.
I still am able to make the switch back to my middle finger for certain tunes, Dowling's "Bottleneck March" for instance.

My point is that this stuff shapes what you can and can not do, and that nothing is "right" per se.
This is a pet theory of mine, and if you look at old footage of early blues players, you'll see
that they each had their very specific and often idiosyncratic way of playing - and that this was a great thing,
since it meant diversity and personality in style. Cultivate your idiosyncracies, I say, but be open.
I had to switch when I heard what Steve James could do with his technique,
so sometimes the desire to learn something new and expand your arsenal of licks decides for you.

I recommend the use of fingerpicks to maximize the sonic potential of the resonator guitar, but I also
sometimes enjoy playing them barefingered, snapping and punishing the strings, or just playing them quietly.
There are no fixed rules about this either, but I will say that fingerpicks are a great tool in my opinion.
When I first learned my way with them they felt terrible, but I encourage you to persevere -
the sonic payoffis well worth it. Go slow and let the muscles learn how to adjust to the picks.
As a student of Steve James, I use thumbpick and two finger picks.
I used to use three, but I found that the ring finger just tended to get in the way and create more confusion than benefit. I find thumb and two fingers to be an ideal combination, sometimes alternating with just using the thumb and index -
this is great for heavy Delta blues, a la RJ.

Open tunings are at the core of many country blues sounds, and I recommend that you explore them.
I use open D and G. These are structurally similar, but yield vastly different affordances. Open D is beautiful,
lush and dark, open G more tense-sounding but also very compelling. I find them both very inspiring,
but in quite different ways. For me, open D means sounds that are broad and dark, yet because of the tonic
on the high D string, very melodic. Open G feels like a somewhat narrower sound to me, yet it can
afford lovely close-voiced, almost dissonant sounding chords, and it is, of course, a lovely tuning for
heavy rythmic Delta blues sounds. Check out Rory Block for the last word in this style nowadays.