Most of the rest is repetitive to do and needs to be left alone overnight. Perhaps longer if you applied the sand paint and glue mixture to thickly. THEREFORE do it somewhere it will not et disturbed, that is dry and no one else wants to use and NO ONE minds if it gets dirty. IT WILL>
Mix up the paint, glue and a small drop of water. You will know how much water with experience, and the only way to get experience is to do it! As a staring place I would suggest a LITTLE water. As it is just to thin the paint and the glue. I Try to use about 1 part water to 6-8 parts paint, it all depends on how much glue is already in the mix.
DO NOT try to brush the sand off!
Wait overnight (at least 25 hours preferred). For some people (Author looks sheepish) this is the hardest part
Repeat as mentioned above a MINIMUM of 3 times. (each time does make it stronger, BUT you do lose a little definition. So Plan on it taking 4 days MINIMYM.
Remove excess sand at each coat. I find simply tipping it works very well. Repeat the tipping on all sides to make sure you have all the excess sand off before starting the next coat.
Keep the sand safe and use again on later coats.
If it is clumpy It has not had long enough to dry. Which means It has had too much water in the mix! If it is clumpy leave it alone for 2 more days (Perhaps longer is the weather is wet>.
When you are satisfied (remember a minimum of 3 coats and ample drying time). Paint it with emulsion paint your base colour. feel free to water the emulsion down a LITTLE as it then gives better coverage. If you water it down to much it will need 2 or perhaps more coats. (But usually not)
The final stage is to dry brush the op colours on. I use a 3" or 4" brush for speed Bought in a pack from Poundland.
You will need to work up through the layers until you get to the highlight coat. So while you do TRY to keep brush marks out it is not a complete disaster if some occasionally show in the early stages.
This stage should not take long if you have all the preparation done. If you start to early the sand will clump and you will struggle to get a good result. But I honestly finished the painting of both boards at this stage within 30 minutes. Preparation is the key and waiting for it to dry properly is VITAL.
DESIGN: When I made my first boards I had too many craters. So be aware of that. These boards have far fewer and are designed to allow other terrain features to be added later.
Finally:These 2 boards bring my moonscape (as I call it) up to an area of 6 foot by 4 foot. And if need be I could make it MUCH larger, limited only by time, storage and money. Ido not at this stage need a larger area so 6x4' is where (at least for now) I will stop.
Thanks for looking. All the best Clint