I'd like to get a similar vintage/retro blur look shown in these images below, using Adobe Photoshop.
What would be the best strategy to use to mimic these images effectively?
I see no blur. There's more going on here I think.
This is a quick and easy vintage photo effect for the most recent version of Photoshop CC. Convert the image layer to a Smart Object, and apply the Camera RAW Filter. Click on the Presets tab, and under the Creative presets choose Vintage Instant, and under the Grain presets choose Heavy. Or go wild and try out as many presets as you want!
The images you have provided have a slight blur because they are photos of photos which are slightly out of focus. The grain you see and some of the discolouration is from the printing process and natural ageing of the materials used.
To mimic this and produce a retro look do the following.
This is best done with smart filters.
If you have no LUTs that work well, you can use a top layer of colours then use blend modes and opacity to create similar effects.
In the below example, I painted green orange and blue on the screen, then gaussian blurred it, then applied the Multiple blend mode and reduced the opacity to 52%
*In this final version, I prefer my own retro colour adjustment over the Photoshop LUDs. However, some plugins are very good at this and would do a better job.