I'm mainly a painter so i'll chime in on this one. I have some warriors are up in the aphotic gallery, and i'll be starting a full project log soon, which will have a lot more of the stuff i've done in the last 4 weeks or so. Also, go through that section of the forum there are some amazing DE painters that post here and none are afraid to let you know what and how they did something!
1) Do not overload your brush with paint. If you have anymore than 40% of your brush covered in paint, you have too much on; it'll spill onto place you don't want it and you'll have that smear effect you want to avoid.
2) Although TG over uses this expression a lot; water down your paints. 50/50 paint/water - this is for a few reasons. Flow aid, so you don't end up with blobs of acrylic for that smooth finish, and it makes the colour more translucent so it 'blends' (all painters always looking for the perfect blend up, or highlight, so you will NEVER master it!)
3) don't be afraid to low light, so with codex grey, water down adeptus battle grey into almost a wash and use a fine detail brush to go around the armour contours. Alternativly use adeptus as the foundation, then pick out the plates with codex grey
4) Use fortress grey as the highlight, simply put, practice makes perfect. Don't give up trying for those nicely straight lines!
here are a few tutorial vids:
Obsidian Rose Kabalites
Last Hatred Kabal
Just take the techniques you think you can do, want to try and just give them a go! In 6 months time you'll look back at you're work and you WILL see progress.