By request here are some tips on turning prepainted plastics into proper minis.
First you need a proper blade... dont mess around with craft knives here, go get a surgical scalpel from your art store. Be ultra careful with these as you can cut yourself down to the bone with ease.
The super sharp blades will cut through the vinyl very easily without pressure, so you can trim back the mould lines with gentle strokes. Always cut away from you, and in fiddly areas try to cut away from details towards boring areas.
Its a good idea to sever the model from its base before cleanup- I use tin snips to do this. For thin footed models I like to leave a little base tab to anchor the figure to my new base. Its better to make big hacking cuts away from feet, then trim back with your scalpel.
To hide the mould lines and fill the slight nicks and ramps from misaligned moulds you can use either expensive liquid green stuff from games porkchop, or grab some acrylic heavy sculpting medium aka texture paste from your art store. This acts pretty much exactly the same but without the green dye. You can add industrial talc or baking soda to make it thicker too. Vallejo do a plastic putty too. All pretty much the same thing. Its really thick acrylic paint medium.
Damp a brush and smooth this goop into the cracks. Wipe it with a wet finger so it is only in the cracks. Once dry, gently brush on more to cover the filled seam.
The acrylic paste can also be stippled on to add texture to parts of the model.
For really thick gaps try slow setting zapagap and sprinkle on bicarb soda. This sets rock hard, so keep this for solid, hefty models that do not flex much.
For any big changes, and to repair any accidentally severed feet, try green stuff (duro-kneadatite) as this is really sticky and flexible so will go with the bendy vinyl. Green stuff, dispite the marketing, it not the best filler in most cases. However here the flex is important.
To strengthen limbs, carefully drill into them and insert a sharpened wire or pin. I usually poke several pins in coated in superglue, then clip off the excess- poken them a little deeper with pliers and fill the hole behind it.
With swords its usually best to snip them off and pin on a plasticard or metal replacement. I use greenstuff and a thick filling superglue like delta thick or zapagap to anchor it into the vinyl hand.
Stripping the paint is possible, but its best to just paint directly over it. If you have to strip, use cotton tips dipped in nail polish remover... dettol won't usually work on this paint. The rubber is easy to damage so go slow!
Rather than undercoat, I just brush evil empire lahmian medium on my models as a base. It one of their few paint products worth every penny. It kills the gloss immediately and gives a nice surface to take washes.
Citadels sadly oop foundation paints thinned slightly are the best paint for recoloring. The current base paints are hella shiney. Go lightly on your paint passes as detail is often soft. I find a light drybrushing of white helps bring out details and helps the layers of paint stick on too.
Finally its a good idea to varnish the ever living crap out of the model... a flexible acrylic varnish is best. Light coats of watered down weldbond will do the trick too. This hardens up a bit too, and I suspect stiffens the model up a tad too... but it may be my imagination- I have not done a side by side comparison as I have yet to do doubles of the same figures.
If your feeling fancy, try sharpening up some of the soft edges. Build up an edge with greenstuff and once its totally dry slice sharp with your scalpel.
I will post some pics of mine later... got me a wicked warband of crocs!