Watch the Charlie's Walk Down online guitar lesson by Fareed Haque from 30 Beginner Jazz Licks You MUST Know
Please don't take the lick names too seriously - I just make this stuff up. Once again, the 6th is important here. Note the chromatic movement from 6th down to 5th. Try incorporating that into your Lick #1 variations.
Double stops are a natural outcome of slightly sloppy, relaxed playing. They sound great and are part of the whole style and swing of roots guitar. Experiment and enjoy, and don't try to make your playing overly clean, this is swing not Scarlatti!
I'm a huge fan of the great maestro classical guitarist John Williams; in many ways one of my guitar idols. But check him out playing some blues - if you really want to, go check out his recording of Charlie Byrd's Blues on Music of the Americas. Very clean, very precise - and just awful. So bad. You just gotta laugh. Clean and precise does not a swingin' guitar player make.
Another related general concept in jazz picking is to use downstrokes on strong or accented beats. Wes Montgomery and others even made this concept stronger by playing big, fat downstrokes (using their thumb!). Now put your pick down for a minute and try it out. You'll notice that it's easy to play a big, fat downstroke. Now try playing an upstroke with your thumb...a bit odd, and certainly weaker. This is important because in jazz we don't necessarily want all the notes the same length or volume; accented downstrokes and lighter upstrokes swing! You'll find it's fun to play with the thumb, many have done so - Wes of course, but also folks like Albert Collins, John Abercrombie, and Sting uses his thumb almost exclusively on bass! It's a good, natural sound, but it can be difficult to play evenly and fast. For the same reasons that it's great for jazz and swing, sometimes it's not ideal for other types of music. Experiment and have fun - find your own way.