Easy body filler to apply and sand?

[burakol]

I am trying to 3d print a Mini Cooper shell for an M03 chassis. Since my print bed is limited in size, i needed to print it in multiple parts and piece them together... in the process, i realize that i need to fill the gaps and hide the supports from the print to make the surface even and smooth.. ive used bondo before on a simple auto body repair i did to my car, but i was wondering if there is an easier product to use and sand for filling plastics other than Bondo

[yogi-bear]

I use spray putty for light surface and auto repair filler for the deeper bits. Plus a dremel with a sanding bit in it to bring it down. Its a bit of work, but I haven't across anything better yet.

[KEV THE REV]

I've also used a Isopon fine filler 2 part mix which is used to repair car plastic bumpers . It's like the Isopon P38 2 part car filler but finer , easy to sand and is made for flexible plastic  . I used it to repair my old King Cab shell , and much more