Firstly, there's no need to go all-in on one range or the other. Everything I paint uses both Vallejo and
GW paints, usually mixed together, and with no adverse effect. So long as you keep your method consistent, there's no issue in mixing ranges, so your
GW paints are not going to be 'wasted' should you decide to pick up some vallejo. In general, I like
GW for their base/layers and washes, and the Vallejo Air range for highlighting or mixing (as it's already thinned).
Now, on to Blood Angels in particular. My method is as follows, with the emphasis on speed and decent tabletop quality.
Prime black
Basecoat: Armour- Mephiston Red, Metals- Chainmail, Bolter casing: black
Wash the whole thing with Agrax Earthshade, Once that's dry, hit the metal areas with Nuln Oil.
Then, re-highlight with thinned down/semi-transparent Mephiston Red, leaving the darker colour in the recesses. Do the same for the metallics with Chainmail.
Paint the eyes a colour of choice (I like green), add some scrollwork with Vallejo Ivory/Sand (along with any parchments), add Chapter and Company badges in yellow. The end result takes about 45 minutes, with 20 of that being wash drying time, and looks something like this:
And welcome to Dakka! Hope this helps.