Yes, earlier I meant the path tool. Sorry about the confusion.
First lets get the basics covered. Then you can move on to using the path tool to create specific designs. I haven't mastered the path tool yet, but I'll cover how I create coloured areas.
I use layers upon layers. This makes it easier for me to alter colours/logos/designs if I wanted to make any changes later in the skinning process.
If you're not using master skinnerz pro kits, I suggest that you use them to help you when making skins.
Now lets say you need to create a tri-colour design on the roof of your FZR.
Lets say you want the base colour of the roof to be blue as in the other FZR you linked.
Select the roof layer from the layers toolbox. Select the blue and colour the roof.
Say you want to create a yellow circle on top of the roof. Now create a new layer (short cut CTRL+Shift+N) on top of the existing roof layer. You'll see this new layer on the layer toolbox; if its not shown directly on top of the roof layer click and drag till it is. Rename this layer as "roof - yellow", so that you'll be able to find the layer easier (later on).
Now, to create the yellow circle select the eclipse selection tool - and create a circular shape on the "roof - yellow" layer corresponding to the FZR roof. Now as the circular shape is shown select the yellow colour and use either the "bucket fill tool" or "paint brush tool" to colour in the selected area.
You can use either the same tool, rectangle select tool or the free select tool to create another shape and then colour it. If you didn't create another layer for this colour, you'll be directly colouring on top of the yellow circle. If you wanted to change the design/colour later - it'll get messy since both are on the same layer; so its wiser to use another layer to draw the shape and colour it.
The purpose of doing that was to show how you can colour in a close-selected area. Lets say you wanted to colour the front bit of the FZR orange, forward of the curve you created with the path tool. You can use the "free select tool" to create a free shape around a specific area and then create a close-area to colour it in.
You can use the eclipse select tool to create curvy - shapes (attached image 3). As I said, I've not used the path tool - and I created the curves for
my XRT skin using the eclipse select tool.
If you want to create a shape and then colour outside of it, simply to go select > invert. This'll allow you to colour outside the selected bit...
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As for the question of rescaling logos; make sure you paste the logos on a separate layer. If you want a logo to appear on the roof, simply create a new layer - rename it logos and paste it to the skin-area corresponding to the roof.
Now if you need to rescale the logo, or just move it around a bit, use one of the selection tools mentioned above (eclipse, rectangular or free select) to select around the logo and then cut - paste it; this enables you to move it around. Once you paste it (and as long as you can see that it's selected), you can simply right click and then layer>scale. This'll scale just the selected bit. When you're playing around with it and is happy with the scale/position right click > layer > anchor (short cut: CTRL + H) to anchor the layer to the "logos" layer.
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As xfirestorm said, its pretty much practise and patience. The stuff I wrote about might sound complicated, but it'll easy when you get the hang of it.