Well here's how!
1) Whine for months until your mum buys you a Fortress of Redemption for Christmas.
2) Leave fortress in its box for approximately one year.
3) Remove from box and build, making sure you leave each section of the fortress disconnected.
4) Spray black.
5) Make half-hearted attempt to paint it starting with a dark grey drybrush.
5.5) Listen to the audio book of Wilbur Smith's excellent novel, Gold Mine.
6) Place the incomplete fortress on the top of your shelving unit so that it's almost impossible to reach.
7) Leave for two more years.
8) Hear that new rules are coming out for buildings and suddenly get inspired to finish fortress off.
9) Realise dark grey colour scheme is a terrible idea.
10) Gaze speculatively at cream-coloured scenery pieces, wondering how you can do it even better.
11) Respray fortress black.
12) Wet-brush fortress dark brown.
13) Keep clippers to hand in case of cat-attack.
14) Watch some TV.
15) Drybrush the fortress light brown, leaving dark brown in the crevices.
16) Lay out Epic Eldar army ready for a game then realise it's never going to happen and put them away.
17) Read Forge World book instead.
18) Dryer-brush the fortress mustard with a lighter touch this time.
19) Lay out dirty kitchen towel squares nearby in case bandage needed after cat-attack.
20) Play Cityfight game of 40k with Tau versus Imperial Guard.
21) Continue painting fortress when its your opponent's go, really-dry-brushing cream, focusing mainly on the upper areas.
22) Ignore death-stares of opponent.
23) Grin inanely at opponent while continuing painting.
24) Use fortress section to provide impromptu cover for a Leman Russ Battle Tank.
25) Pick out detail on Lascannons (Tin Bitz with Dwarf Bronze highlight).
26) Paint other details metal then ink black and drybrush metal for highlight.
27) Pretend you don't notice Sentinel sneaking past.
28) Paint floors in metal.
29) Give black ink wash.
30) Use patented "swirly drybrush" method to highlight centre of each square with metal again.
31) Remark to anyone listening how ass-kickingly good you think it's going to look when finished.
32) Paint missiles dark then lighter red. Pick out tips in light grey and then white.
33) Try to think of witty simile for the way the missiles look.
34) Give up.
35) Do same metal, black ink, metal drybrush trick on other details and pick out skulls in cream and white.
35.5) Wonder why GW put skulls on every single scenery piece.
35.75) Wonder whose skulls they are.
35.8) Wonder if they want them back.
36) Lay out completed fortress.
37) Wonder if strange white shape in the background is headless man hunched over while trying to pick up a dry-roasted peanut that has fallen on the floor.
38) Flee from headless peanut-eating man while continuing to take pictures of fricking amazingly painted fortress.
39) Make deal with headless man that he can go back to looking for peanuts as long as he'll let you take photos of the damn fortress!
40) Realise you haven't actually finished after all because the Lascannon glowy bit hasn't been done.
41) Paint glowy bits turquoise and then light blue to simulate "glowiness."
42) Paint missile bay cover to match Crimson Blades insignia, always sticking to two or three tone painting method.
43) Realise it needs a bit more work.
44) Don't bother to do extra work.
45) Arrange tanks next to fortress in "cool" configuration.
46) Look smug.
47) Continue to look smug.
48) Write blog post, basically so that you can tell the world how smug you feel.