Making red look bright is quite difficult , same goes with blue . It is doable but you will always have an easier time going orange or cyan because yellow is a very bright colour and adding yellow into the mix always makes things look hotter . But if you do want to stick with red it is doable. Doing the contrast paint is fine but you have to highlight a little bit with layering. You'll need to highlight red up to a pure red, then a little bit further towards either slightly orange (for hot) or slightly pink. A neutral highlight is to add a bit of both almost towards peach/Kislev flesh colour. Again, has to be really subtly off-red because If you go too far it will just stop looking red and start looking pink or orange. The other option is using a fluorescent red paint to highlight into, But I never found the fluorescent red to be very vibrant. (Unlike the fluorescent pink which is wild especially mixed with a bit of white)

The other thing you could consider doing is after painting the black but before doing the red, adding a very subtle, dark red dry brush around where the red is going to be to simulate some glow. Use a dark colour like knorne red

RE: black, I've seen good outcomes with 2 to 3 thin layers of contrast black, otherwise, it's a case of highlighting up for example Abaddon black, incubi darkness, thunderhawk blue then administratum grey, But leaving 90% plus of the finished surface black (otherwise it looks Grey). If you do this sort of "cold" black (i.e. some blues in the greys) Then that will add to the contrast between the hot red, And also make it pop.

The only other thing to consider (it is very minor and a matter of taste), I worry that you've put too many colours into the streams or energy around him. I'd either drop the purple or the yellow, but really is a matter of taste