Not sure how actual masking is done, so I juz use which ever I think is good. So thought I should just share my lazy easy method 
1) check the piece that you want to mask
2) Take a piece of scotch tape and paste over the area you wan to paint.
3) use a toothpick to rub through the whole scotch tape, removing any airbubble
4) use a pen knife and cut at the area u want to paint, mainly along the panel lines.
5) After cutting, remove the cut portion
6) Finish off by pasting more tapes on the rest of the gunpla piece.
Now its ready to be painted 
7) Peel off all the tapes after the paint have dried.
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Another Example.. the following piece have been masked
After spraying, Remove the scotch tapes… tada, nicely done
This is just my way of doing it, maybe there are even easier way to do it. Do let me know
simple yet effective!
now i regret getting those yellow masking tapes for modelling. hahaha. =P
thanks for the tip. ^^;
A good idea~
eh when u cut, the penknife will have to be very sharp, esp. for small parts, and in this case, wouldn’t the part be vulnerable to “mis-cuts”?
Yep, make sure the blade is sharp
and cut slowly, especially on round part.
After cutting, use the toothpick to rub the edges again to make sure it stick well
I learn something new every day . . . interesting stuff, I guess this is an example of complicated preparation making the painting itself simpler.
wah nice…….thanks for the tips
Daring skill, use scotch tape o..btw should try tht..XD