How do you use the Rapala Countdown in Canoe Country?

I understand that it allows you to set the depth, but do you first determine the depth you want using a depth finder and then try to set that depth by counting? Or do you use more of a qualitative approach? I'm kind of shallow so I'll not wait too long... or I wait until it hits the bottom and then retrieve...

Does it provide any advantages while trolling or is it mostly for casting?

I use them for casting shallower areas 5-10' deep. Not much use for them trolling.

I count 'em down and then retrieve.

I learned of a modification for fishing countdown rapalas that I am going to try this year. Take the two treble hooks off and use a single open eye siwash hook on the back, with the hook bend pointing up. That way there will be less chance of snagging when fishing it close to the bottom. Haven't tried it yet, but it makes sense as long as it doesn't affect the hookup ratio too much. The mod probably works best on the smaller sizes.

They cast much better than a floating rapala, but I almost never fish them. I like the extra surface strikes I get on the floating raps.

What I do is cast out and then count to 5, and retrieve. Then I count to 7, then maybe 10... depends on how cocky you are. If you are in a canoe you'll have a good chance of freeing a rapala from the rocks (don't pull too hard after you realize it is stuck, that just wedges it in). From shore... good luck moving rocks or logs with fish fishing line.

I fish them like a jerk bait.
L-O-N-G pauses if you want to go deeper.

Definitely one of my go to lures in May (local or BW)
as others have stated cast them out and count them down , just have a feel of what kind of depth is around you.( EXP. you casting out into 16'-20' count them down 10-15+ seconds ) i try straight retrieves , pause and twitch retrieves long sweep type moves and a combo of all
as far as modification go for it , i modified mine *(CD9's) never liked the trebles so i replaced all of mine with Gamakatsu's , and took a dremel tool to this one and added some super glow paint , it's already been hot with bigger crappies this year :)