I'll add my comments just as reassurance.
PBL Coating booster alone is an excellent LSP with gorgeous water properties, easy to apply, great durability and gives wonderful shine as well.
However, Booster really shines when applied over PBL Coated cars. The hydrophobicity of the coated car is taken to the next level.
After boosting, many customers comment their cars looks even better than when first coated.
I generally do the first booster application after 1 month, and this is the time I generally hear those kind of comments.
My procedure is to do a thorough wash, dry and boost.
If customer faced severe contamination in between those 30 days (like overspray, etc), I may do a light clay, re-do the Cleansing Polish using a finishing pad (to remove clay marring and improve surface cleansing) and apply the booster later. I may avoid using polishing pads for this procedure to keep me from 'scrubbing' my coat, which would reduce it's longevity.
To apply the booster, I prefer a MF towel. Spray the towel with a fine mist, spray the surface to be worked, and spread it front to back, side to side, until it turns clear (~2 or 3 towel passes).
Immediately buff excess off, or not longer than after doing a whole panel.
At the end, I may do a last buff to get a streak free booster application.
You'll be amazed by the results, hands down.
Topping the coating may negate it's properties, but it's temporary, and if you are topping it with a quality product (like Synergy, Souveran Wax, etc) you will get the wax look, in a glorious manner.
That's because the coating will fill microscopic tiny pores, leaving your surface not only well protected, but smooth and plain. This defect free, smooth surface is a good 'bed' for a layer of your favorite product.
The sacrificial layer will be your quality wax, and your coat will be well protected bellow. That said, your finish will be down there, away / far from the elements action, and I believe this is the purpose we protect our / customer's cars, and always look after more, and more...
In advance, whenever your wax wash out, you'll not be left unprotected (like relying only on wax protection), but the car will come back to coated state (the coat will hold strong there).
That said, I don't see disadvantages of topping the coating, in contrary, using quality products will give you visible improvements.
Also, I'm suspect to talk about the booster, I simply LOVE it and use it often on my customer's PBL coated cars.
PBL may not even need to be boosted, because it lasts longer than any other wax or sealant I've used. However, the booster just works, improving the PBL coating in many aspects. Worth every penny, and full application may take you 10-15 minutes.
Detailer's Tip: coating booster is a great LSP for door jambs, easy and fast to apply, giving them a smoother feel and easy cleaning afterwards.
Please, let me know if you need any guidance regarding coating application, booster application, etc, it will be my pleasure to help you out.
The cleansing polish may also be used when you applied a layer of wax and wants to get rid of it. Cleansing polish rejuvenates the coating, and booster, like it's name says, will boost it.
I use all those products in a regular basis, and I only have positive results with it.
Good Luck,
Kind Regards.