OK - I've tried the Ond method for a mirror finish on the inside of my bartop project's side panels (the visible parts). All in all it worked great and very happy with the results! You can see the stages and some pics in my
project thread.
Up until now I've never really thought about proper prep and quality of finish so this whole process was pretty much new to me (I'd only done a bit of filling/sanding/painting on my Jimbovision project but only on surfaces that were to be hidden by vinyl artwork). I can honestly say I'm a complete novice at this.
Here are my findings: -
- Don't underestimate the amount of patience and elbow grease you'll need.
- With the auto primers/paint I was using it needed 24 hours at least for each coat to dry. These 2 panels took me almost 2 weeks from start to finish.
- Get a decent mask - the filler I used (Isopon P38 body filler) and the Auto Primers/Paint STINKS.
- I was painting marine plywood. I needed 5 coats of high build primer with lots of grain filling and sanding in between each coat to finally get rid of all the grain marks. Where the plywood surfaces reached the edge of the panels (where the saw cut them) I needed lots more work filling chipped away bits from the messy cut.
- I found that when I wet sanded with 600 grit (with a sanding block) on the HB primer, I had to go REALLY lightly. Around the edges of the panels in particular it was very easy to completely remove the primer back to bare wood.
- Definitely use daylight for sanding if you can, and as Ond says, check your work regularly. It's easy to sand too much and then a torrent of bad language ensues. It wasn't always easy for me to use natural light as I could mostly only work on this in the evenings, so I used a strong lamp shining on the surface, which I constantly had to move about along with the wood. It did enable me to see the work clearly and see where needed more sanding, but it was a pain. Natural light would have been much easier.
- Get lots of rags... seriously Ond - do you have a lifetime supply or something?

I went through LOADS.. they get very dirty very quickly.
- I made some mistakes when spraying that meant I needed extra coats of the HB primer. I tried spraying vertically down with the work underneath the spray... bad idea... this caused drops of paint to fall on the work from the nozzle of the can. Also, I found I needed wipe the nozzle regularly else these drops from around the nozzle would be pushed out onto the work by the spray. I found I also needed to increase my spraying speed as if I went too slow too much paint was deposited and it began to run. Lessons learned here. Definitely advise practicing on an offcut first! It took me until the actual topcoats of paint to figure all this out!
- Wet sanding actually feels really nice... LOL... it has a nice kind of resistance to it that is very satisfying... I'd never done it before.
- I used Maguire's Ultimate Compound instead of their Swirl X as Ond used in his video. It seemed to do the same job and had great reviews... and when I used it the surface came up great

Thanks Ond - I feel much more confident for when I start the other panels in my project. Learned a lot doing this! You are indeed the man.