please help with wood filler

[camele]

hi every one i am curently building a lightning mcqueen bed for my son ( on a very tight budget) and i need a little advice i need to fill and round the top edges of the bed. they need to b strong and curved i was planing on doing this by using timber to fill most of the gap and then using auto body filler to do the rest but i went out on the weekend to get some and i couldn't understand how it has gone up so much since i last bought it is their a cheaper better option out their ?
thanks camele

[elanjacobs]

Try Builder's Bog

[Master Splinter]

If you are trying to round off the edges of the timber (MDF I presume) a better solution would be to use a router to get the desired profile on the edge. On a cheaper budget, you could fake this with an orbital/belt sander if you had one handy. (do the sanding outside, MDF dust is not nice).