How to get a smooth surface?

[traveller]

I am building a rather basic terrain board with a slight hill to play a Gandamak 1842 scenario. The foundation is EPS covered with a mix of filler, glue, paint and sand. For some reason I got the mixing wrong so the surface is too rough. I need to make it a bit more smooth and even and then add gravel and rocks to make it a bit afghanistani. I would be grateful for any advice how to smoothen it in the best way. Is filler the best remedy?

[rebelyell2006]

Wood filler or spackle.  It goes on really smooth if you get your fingers wet first.

[SBRPearce]

If you need to knock down the existing rough surface to smooth it before the application of filler, my best suggestion would be to get some aggressive sanding paper (60-80 grit) and wrap it around a wooden block to grind off the rough spots. depending on how rough and how durable the surface, wear a glove - I once tore up my hand trying this trick with A) bare hands, B) no sanding block, C) over-enthusiastic scrubbing.

[Silent Invader]

One thing you can do to smooth a surface is use very fine beach sand (or play sand, or similar) with waterproof wood glue (Evostik exterior in the blue bottle) and a tiny amount of water. You can brush this gloop onto the rough surface and 'wipe' it into the gaps etc.

[Mister Rab]

I've found that mixing water into spackle/filler until it is yoghurt thickness and then brushing it on liberally with a cheap wall-painting brush gives a lovely smooth surface. In fact I was doing just that yesterday!

[traveller]

Great suggestions!

Many thanks for you help!