Not a problem. Most of my smallmouth fishing is on rivers, but a lot of the same baits carry over. How you fish them, however can be a lot different. Also, being comfortable casting big flies is a bunch different than casting dries or simple nymph rigs. Practice make perfect, and make sure you're comfortable opening your loops up, double hauling, and roll casting with bigger flies.
A 6 Wt will throw a lot of patterns, but most of my smallmouth fishing on the fly is done with an 8 wt. if you can grab one, it can save you a lot of frustration, especially with larger topwater flies like deer hair poppers. Also, I would suggest picking up a sinking line or at least a sink tip, otherwise getting down to fish will become a problem.
On top, I like deerhair poppers, though they can be tough to cast on a 6 wt, especially after taking on some water. Small size 4-6 foam poppers also work well, and there are tons of mouse options, as well. For most top water stuff, I don't really like long leaders (it can be super hard to turn over flies for me, especially when wading) and I'll usually keep them from 3'-4' for most top water fishing. I tie my own with Big Game or Maxima and generally run these tapered down from 40lb to 10-15lb. Usually the formula works out to 50% 30/40lb butt, 25% 20lb, 25% 10/12lb.
Flies like Dahlber Divers can be fished with a floating line similar to a floating Rapala. This can cover water well anytime fish are going to be feeding up and active. Again, think floating jerk bait.
A lot of my smallmouth fishing, in either lakes or rivers, I find them relating to the bottom more often than high in the water column most of the time. (exceptions include when they're busting up on baitfish like alewives/shad or juvenile perch) So, I do like flies that I can get down with a weighted line versus a floating line with a 10'+ leader. (Casting heavy sculpin or crayfish patterns on long leaders is not a particularly enjoyable way to fish because it can be so hard to control.)
When I'm fishing jerk flies (unweighted baitfish patterns) I like a sinking line and 6' or so of leader. This can be killer in lakes because they tend to be more or less neutrally buoyant and you can fish them like a swimbait. (think Deceivers, double deceivers, anything with synthetic unweighted bodies, and tall but narrow heads intended to swim smoothly versus kick tons of water and push hard to the sides.)
For slightly weighted, but still neutrally buoyant flies with deer hair or similar heads (think D&D, Sex Dungeon, Zoo Cougar, etc), I like a sink tip or sinking line (depending upon conditions) with 4-6" or leader. The D&D and Sex Dungeon type baits may be tricky to work well on a 6wt, so stick to smaller sizes - they can create lots of drag on the cast.
For jig flies like clousers, Grumpy Muppets, etc, a floating line can work well, but you'll likely want to extend your leader 6-9' to make sure you're getting down well, but still keeping a good connection to the fly.
Dredging with bottom contact baits (dragging sculpin/madtom/goby patterns or crayfish) usually requires a full sinking line and depending upon conditions, the technique can range somewhere deep nymphing to slowly dragging a Texas rig or jig.
As for colors, just pick colors that mimic what you would throw with conventional tackle. The same general rules apply. Make it look natural, mimic forage, or when conditions call for it, break out the bright colors and flash.
Does this help? Sorry, I don't have a suggestion for a walking bait substitute, but maybe @Further North can make some recommendations.
