Ephereal Photo Editing with Photopea

Use photopea.com.

1. Position photos roughly where transitions are wanted.
2. Select an image layer - select “add raster mask“ from manual search,
3. A white thumbnail will appear next to the image in the layers. This is the mask.
4. Press b to activate brush. Select the mask thumbnail that appeared. Press x to swap to foreground removal (or switching brush to black).
5. Select the brush preset. Set a low opacity and increase brush size.
6. (Optional) You can add a slight gain to further replicate the effect. Add a blank layer, 50% gray. Select Filter → Noise → Add Noise (3-6% Gaussian, Monochromatic). Select blend mode layer to overlay, 30-40%.