Re: Getting started
If you are determined to combine watercolour with your soft pastels, then Art Spectrum isn't ideal really, it doesn't "take" the watercolour brilliantly because it is a plastic surface. You can put some loose washes on, but thats as far as you can go really. I used to use felt pens on my Art Spectrum, they worked fine, and if you use the ones with a broad "nib" you can make nice big areas of colour if you want.
If you want to begin with watercolours for sure, then I recommend you use a HOT PRESSED watercolour paper, rather than a NOT surface which has lots of bumps. The Hot Pressed will take the watercolour beautifully, and then you can add soft pastel over the top, but be aware that you cannot overload the paper with too much pastel because it doesn't have masses of "tooth". If you are careful tho, your results should be good.
Somerset Velvet is good with watercolour too, it is nice and heavy.
The other alternative is to "stretch" a piece of regular pastel paper, like Mi Teinte, which is commonly available in Australia, I believe. You dampen the paper on the back with a sponge, lay it onto a wooden board, and tape down the edges with sticky brown parcel tape, the kind you have to wet. Leave it to dry, and it will tighten so that you can use watercolours on it happily.
If you choose to use watercolour paper, and it is a light weight, and you want to splash around, that too needs to be stretched, cos it will buckle with lots of floaty watercolour on it, but with watercolour paper you must dunk it in the bath for 5 minutes, shake off most of the water, lay it onto a damp wooden board and then tape the edges down. Leave it to dry naturally, flat, and it will be tight as a drum when dry and you can splash about to your heart's content.