Masking the Cockpit tub and canopy.

For the canopy try bare metal foil, simply peel backing gently burnish the foil over canopy, thx to my wife I use a rubber cuticle pusher it works extremly well. Remove area to be painted with a freshly honed or better yet brand new hobby knife blade. The only down side would be cost, but Im sure its cheaper then a mask. Good luck.

QUOTE: What is the best and easy to use material to cover the cockit tub are while painting the rest of the aircraft?

If you are asking how to mask the cockpit without the canopy in place, then here goes...
I usually fill the cockpit with a trimmed piece of index card, balled up paper, or facial tissue and then use silly putty stretched over the paper to fill the voids and seal the edges. The silly putty is tacky enough to hold on to the inside of the cockpit, but not so tacky as to damage the paint or delicate instruments. It also does not leave any residue. The silly putty needs to be carefully removed because it does get a little dry over time, but with a little care, I have had not trouble removing the putty from cockpits that have beens sealed for a month or so. I prefer using paper instead of facial tissue, because there is less lint with paper versus facial tissue.
Another method I have used to seal cover a cockpit is to stretch either tape or Parafilm across the cockpit. The tape or parafilm is then trimmed around the cockpit. In my hands, this method works OK, but I have a hard time getting these material to adhere (or seal) precisely to the inside edge of the cockpit and end up with little gaps that either allow overspray in or require touch-ups later. The Parafilm will contour over the irregular shapes that may be higher than the edges of the cockpit better than the tape, but I still have trouble getting a good seal on the inside edge.
I have also used cotton balls to fill the cockpit and then cover this with tape, but I find the cotton balls leave too many small filaments in the cockpit that I end up removing for days and days or discover dangling from instrument panel to the seat harness as I place the model on the display stand.

QUOTE: Can anybody please share their secret in masking the canopy ...

I think that using bare metal foil (BMF) is usually the best method to mask a cockpit. It may not be easy, but it certainly does produce a good result. However, you will need to be careful and sober to get a good result (see topic in this forum http://www.finescale.com/fsm/community/forum/topic.asp?TOPIC_ID=11187). I will apply the BMF to a non-Futured canopy. I fear that the BMF will pull off the Future, unless the Future is very well cured, so I apply Future after the canopy is painted. I will cut the BMF into 3-4 mm wide strips about a long as the canopy is wide and then apply these to the canopy. I try not to have more than 1-2 layers over the area of the canopy frame were I will be cutting since this results in the need to apply more pressure when making the cuts. After placing the BMF on the canopy, I burnish this to the contours using a cotton tipped applicator (Q-tip/cotton bud). The small strips of BMF will contour nicely to a curved canopy. You then need to trim the inside edge of the windscreen/canopy frame to create the masked area for the windscreen. Using a new, sharp blade, (I use either a number 11 blade or a utility knife) and taking ones time, carefully cut along the junction of the windscreen and the canopy frame. Of course, this requires that your canopy has a raised canopy frame! If during the cut, you feel as thought you are going to err, err toward the canopy frame side of the cut as opposed to the windscreen side. This may result in a fine line on the canopy frame, but this is easier to fix than a scratch etched in the windscreen. Apply gentle steady pressure and with a sharp blade you should be happy with the results. I have tried this method with Parafilm and tape, and I feel the BMF results in a sharper edge and a more durable mask that stands up to handing and manipulation better. I have also had no trouble with removing the BMF afterwards. I remove the BMF with a fine tweezer and patience. I have heard some have had problems with residue left on the window by the BMF, I have not had this problem. But this is another reason why I don't Future before masking. Tape masks have left residue afterwards in my hands.
Sorry for how long this post has become...must have been that fourth cup of coffee!

I use damp tissue paper for inside the cockpit. for the canopy I use baremetal foil.

Providing the cockpit has a nice flat sill, and there's no seat sticking up, I just seal it over with a piece of scotch tape while I paint the rest of the model. Sometimes I glue the windshield on first, seal the cockpit and back of the windshield frame with tape, and mask the windshield frames with tape. Then I can paint it at the same time as the plane.