Here's a go at a quick tutorial, just pics. I use only GW paints because I became familiar with them before I realised I had other options out there and so have doggedly stuck with them ever since.
First off here are the colours I use, the vermin brown can be used to line highlight at the end if the orange is too cartoony and bright for you. I use vallejo game colour thinner (its not a paint!) as I find its easier to work with than water when thinning down paints. I like a Black undercoat because I am lazy about filling in the black later and the dark undercoat provides a good contrast with my bright final highlights. Step one is to base the guy in chaos black, I use spray and fill in gaps with a brush once its dried.
Step two is to layer up with mechrite red. I thin my mechrite red 1:1 with paint and thinner. You could use water instead or as well as thinner this means no detail is obscured. I like to layer up with around three thin coats. As you can see in the picture the pad on our left has been fully painted and the head and the right shoulder pad are in the process of being layered. Ensure layers are completely dry before painting the next layer over it or horrible things happen. You can be quite messy with the mechrite red, after all your going to shade it and paint any detail later. Once the Red is dry wash it liberally with Leviathan purple (if you want it really dark you can use badab black or thraka green or even a combination in different layers)
Layer up with blood red, again thinning 1:1 with thinner. You can start to cover less and less of the recesses of the model and concentrate more on raised areas each layer to leave shaded areas and create a smooth blended transition in a way that wouldn't be possible if you painted the model with just one layer of each colour.
Another layer or two of blood red, solar mach orange and thinner mixed 2:1:2. This is because the orange foundation paint is much less transparent than the other paints. If you were to use blazing orange or similar you could ratio 1:1:2. Again paint less and less of the mini with each layer to leave shading. Once this is dry you can use very controlled layered washes of leviathan purple to correct any areas where not enough shade has been left of you've accidentally dropped some lighter colour where you didn't want it. Don't just smother the whole mini in wash here though or you'l dull your highlights. If you wanted to tone down the orange you could wash all over with baal red.
Paint up the rest of the mini and then finally do fine line highlights with solar mach orange to 'toon him up or vermin brown if your going for a redder marine. I leave these 'til last as they can be more of a pain to fix later than your layered red that you can just touch up and wash down in case of any mistakes. I use the side of my brush to paint most of these fine lines and just draw along the edges as its just easier to keep a controlled line of even thickness that way.(Finally you can chip over if you like to weather your marines, I use charandon granite feathered on edges and then feather boltgun metal in leaveing a thin edge of the granite colour showing. Its a great way to hide mistakes! it works particularly well on very bright or black models for contrast).
Hope this is of some use to some of you out there!
Also here are some links to youtube vids of different ways and techniques to paint red I found helpful as I realise my picture only stuff leaves something to be desired! I've given you pt 1 of each so just look for the next parts in the sidebar for more, first three are from 'girl painter' the last is from 'spuse maroon':
Blood Angels Commander:
Blood Angels Terminator (from Pt 2, as part one just undercoats it white)
Blood Angel RAS Marine:
Blood Angel Tactical Marine