Next, we're going to add a shockwave effect, pushing out very quickly from the centre of the effect.
For this add an adjustment layer, apply a bulge effect to the layer and move the bulge centre to the centre of your explosion.
Increase the horizontal and vertical bulge radius to as far as you want the shockwave to reach. This bulged layer will shortly become visible underneath our shockwave matte which we will create next.
Create a new solid and place it directly above your adjustment layer. Add an iris effect to the layer and increase the iris points to the maximum (for me that is 32) to make it as round as possible. To create a ring around the opening of the iris, add a colorama effect, set the input to alpha and the output to ramp grey. Then drag the white colour selector on the colour wheel to 6 o'clock and add two black markers around 11 and 1 o'clock respectively.
You should see a nice white ring on your shockwave matte
Next, animate the outer radius of your iris so this ring expands away from the explosion centre like a shockwave in around 10-15 frames. Additionally, keyframe the opacity of this white ring to go from 100% to 0% as it expands. Ensure the layer starts exactly at the moment the explosion kicks in.
Then set the Track Matte option on the adjustment layer with the bulge effect to Luma. This tells the adjustment layer to derive its opacity from the brightness in the layer directly above. Notice that our solid with the animated ring has become invisible, but that instead we can now see a bulged shockwave on the screen
Finally, we can add some camera shake to the explosion effect using a simple expression in Adobe After Effects!