With regard to the Lansky (or GATCO), the clamp will work with most FFG blades, the only possible exception being those that are both SHORT and very thick, with an extreme taper towards the tip. A FFG blade like the Spyderco Military (or Para) is a cinch to set up, by comparison. Most blades have a relatively flat or shallow taper, at least in the rearward 1/3rd of so of the blade (towards the tang). That's usually where I position the clamp. The key to the whole thing is patience, and paying close attention to the contact area between the clamp & blade.
Some things that have helped me a lot with the clamp setup:
1.) Use masking tape or painter's tape underneath the clamp jaws to minimize the chance of slippage/movement. Another thing I've tried for this, use a piece of med/fine wet/dry sandpaper with the BACKING against the blade (to prevent scratching), and the rough side against the clamp. This works particularly well if you are sharpening wet (with water or oil). The backing of the sandpaper is surprisingly grippy against the blade, especially when wet. And obviously, the rough side against the clamp will keep the clamp from slipping against the paper. Sometimes the masking tape or painter's tape will slip or move if wet.
2.) Get some longer screws with low-profile heads (size 10-24, in lengths between 1/2"to 1") for the clamp. The 10-24 size is commonly available (I get mine at Home Depot/Lowe's). You can also get these in brass, which helps to minimize digging into/damaging/stripping the aluminum clamp, as steel screws will do.
3.) When initially positioning the clamp, first pinch the forward end of the clamp against the blade with your fingers, so the clamp's jaws are flush with the blade's sides. Then, just finger-tighten the forward screw (nearest the blade), until it just starts to snug up. Then, adjust the rear screw until it just begins to tension up against the bottom side of the clamp. Maintain finger pressure on the clamp as before, and use a screwdriver to gently tighten the forward screw a little bit (quarter turn or less), then do the same with the rear screw. Alternate back & forth this way until you're sure the clamp is snug & flush against the blade on both sides.
4.) I NEVER USE the narrow, milled notch at the forward end of the clamp. It's too shallow to hold the blade effectively, and it's not accurately milled either. Tends to 'tilt' the blade up or down when clamped, which results in mis-matched bevels (wider on one side, narrower on the other). I always position the clamp so there's at least 1/8" - 1/4" of the clamp's (un-notched) surface against the blade, depending upon the blade's width.
I've reprofiled maybe 15 -20 knives so far with my Lansky & GATCO sharpeners. Using the tips & method above, I've not had any major setup issues with the clamp. Just be patient, and take your time to set it up. As per proper sharpening technique, use light pressure with the stones. That will also help to ensure there aren't any slippage/movement issues with the clamp.
Obviously, the Lansky or GATCO are better suited for reprofiling tasks. For general edge maintenance, a Sharpmaker or something similar will do fine. And for light, daily touch-ups, stropping is always good.