I used acrylic paints with acrylic paint retarder mixed in for the translucency when I did backglass touch ups. Then after I was finished with the touch ups I would use Americana Light Buttermilk with air brush medium mixed in to give it the "diffuser" type quality you're looking for. and on the opaque areas (grey paint on back to keep light from shining through) I used Sky Grey (I believe it's been awhile since I've done any touch ups for anyone!) Then I would spray another light coat of Triple Thick to seal your touch ups in.

Phoebe

I should've said that most of the glasses I did were Williams early solid state or EM's... Yes I did use airbrush some of the time depending on how much touch up was done on the glass. If it was small areas I just used a brush. Alot of the time I found it was easier to use a brush than deal with masking everything you don't want painted.

Phoebe

I did a Scorpion and used white primer. I thought it looked really nice and held up for the next year plus, but now Inlost track of who has the game.

I actually have a light table that I worked on glasses on...So as I was doing the touch-us I could turn it over and check my matches. If I didn't like my match since it had been triple thicked I could go back and wipe it off and try again...Alot of the time it was lots of trial and error. That's one of the reasons I would always Triple Thick the glass before I would start the touch-ups. I also had all my paint colors on clear panels so I could compare the paint over the spot I was touching up. The paint will dry darker than it is when wet so that needs to be taken into account as you go as well.
If you're worried about the white layer not matching you can put a coat of Triple Thick over your touch ups before applying it then if the white layer is not to your liking you can remove it. It's always good to test in a small area before doing the entire glass to check your color matches.

Phoebe

I'm not sure but my guess is they don't. I can't speak for anyone else I commented on what worked for me with good results. Like I said it was alot of trial and error and experimenting with how much retarder or air brush medium I put in...I used to use 1 drop of paint and 2 drops of retarder as my base line...when I had it mixed to the proper translucency to match the area on the glass I was working on. The consistency of the paint was about the consistency of milk. I didn't paint as I did kinda of put a dab of my mixture then (because of the retarder) it would flow into the areas I was trying to repair this also helped with brush strokes...

Triple thick doesn't act as a diffuser. All TT does is seal in the original art and your touch ups once you are finished.

All I can say is that you can touch up a backglass and make it look great! BUT it will never look "perfect" if you want perfect then you should probably either find one in better shape or pick up a reproduction because it will never be exactly as it was when it first came off the line.

Phoebe

While this does not cover the diffuser layer, I do discuss some failures and successes with airbushed Createx and 'my' process.
You might get some info from it, start at the link below, some info before and some after, but a good starting point should you wish to explore.

https://pinside.com/pinball/forum/topic/polishing-up-a-silverball-mania/page/2#post-3883923

I had a pinball party early this year and friend gave me a copy of Michael Shalhoub's book on pinball and I really enjoyed paging through it and remember reading about a gal named Phoebe who did fantastic work on playfields & backglasses; great reading and story.

I'm involved in auto body so I spray my backglassses with auto clear coat & do my touch ups from there but it's very hard to get really nice results and it takes alot of time and like you said if its not good just wipe it off and start over. I do like your idea of adding the reducer to the paint and let it "run into the damaged area"; I'll have to try this as the brush marks show up and with the reducer it should be more translucent.

Thanks for sharing some of your techniques.

Yep that would be me Thanks for reminding me about that !! I met Michael and Alan at Expo 2006 and they contacted me after going back home about doing some games for them. They would buy them here in the states, have them shipped to me I would restore the game and then at some point they would have a container delivered and they would come over. We would load up the container with the games that I did for them as well as others they had picked up to fill the container and then it would ship to them I did around 19 or so games for them. From around 2001 till about 2012 I did maybe 2 or 3 hundred backglasses for people and hundreds of PFs. I did try a few different sealers for BGs but never tried auto clear on BGs.Triple Thick always ended up with the best results for me. I know some people have had problems with it and a couple that I did got stored in non temp controlled areas and didn't have good results for them. Again I think alot of that is the way it's sprayed. It takes some trial and error to not spray it too thick and just lots of variables go into it. I did start shooting auto clear on PFs when I was winding down doing restores for other people in 2012. I still do my own games and I paint custom stuff (figures) for games and every once in awhile a close friend will convince me to do one for them but I'm enjoying my "retirement" and just enjoying playing my games!!

Phoebe