What type of cement do you use? And should the final product be flexible?

I basically use this method

http://cs.finescale.com/fsm/modeling_subjects/f/3/t/157928.aspx?page=1


This was a good one,but the pic links are broken.Just Google Dragon Magic Tracks Tutorial,you will get a myriad of videos and links to show the way.There were probably some here also that I cant find.

Type of cement/glue depends on the material that the links are made of.
Styrene -> I uses the same solvent type as for the rest of the kit
White metal -> CA or epoxi

I assemble stiff sections and then glue the sections together to make the largest piece that I can still manage to get onto the running gear. I usually end up with a VERY deep U and a shaort curved section to close the gap over the sprocket wheel. That last little bit is 3 to 4 links long. The deep U goes from 2 to 3 sprocket teeth onto the sprocket all the way around and over 2 to 3 teet on the other side.
Test with two links on the sprocket first and check that they can be pulled off and put back again, then try with three links et.c until they start jamming.
I shape the upper run to get the correct or desired sag, note that some types of track have no visible sag.
The short bits from the "ground" up to the idler and sprocket are used to adjust the length of the track to get everything to fit, they can be given a slight outward curve to adjust for the length of one track link.

When you're done you can easily remove the tracks from the hull for painting then reattach the tracks to the wheels?

Yes. As long as the final one or two sections around the sprocket are not glued into place.
I usually paint the various sections before building up that deep-U, just leave the mating areas, half of a link on each side of the joint, free from paint and paint those when the deep-U has been assembled.
I don't shape or build the track sections on the running gear except for the top run which may need to sag down a little between the return rollers. It depends on the type of running gear and type of track, live vs dead track.
A Panther, T-34 and M113 are almost the same but the sprockets on the Panther and M113 lift the track more than the sprocket on the T-34 (which is nearly level).
An M-47/48/60, Soviet JS-tanks can be compared with a Pz III / IV, sprockets front vs rear but they all have return rollers. The top run on the US tank will be very near straight, on the panzers it will hang down a little bit, less than the thickness of a track link and on the Soviet tanks the track can sag more, not always but it happened.

When I am ready to start glueing the track to the running gear I clear the paint off from the spots where the links touch the roadwheels and return rollers and use a solvent glue to to fix the track to the wheels. The sprocket usually doesn't need any glue but I do it anyway to prevent that short little section of track from disappearing
/ Robin

I have yet to try single link tracks, but this is good advice Robin.