get fusor 147 and put it between the skirt and the body of the car, and put in stainless steel self taping screws to let it cure over 24 hours. To fill and make it look molded you should probably get some duralgass or everglass and fill in the edges, and feather it to make it look stock, sand it, apply some rage extreme or light body filler, sand that, then glaze it, and sand that and primer it. Thats a pretty basic decent how-to. Get crispy to chime in, shes the one whos given me all the advice on my bodywork.
It may sound easy, but body work is a little harder than it seems, trust me ive started to do my own... but you could do it yourself, it takes patience, long hours and dedication.