I dont think "priming" the pad would be an issue. The OP stated he was merely applying Menz PL, a sealant on speed 3 with no pressure.
Usually when applying LSP's, especially sealants, I find it unecesary to "prime" my pad. Pad priming is usually done when using compounds and polishes. When dealing with higher DA speeds (5-6) with a cutting/polishing pad + abbrasives, you want the product to work instantly for you, and to have constant lubrication between paint & pad.
When applying waxes/sealants, not so much. You always want to use a soft foam pad designed for LSP's. Why would you prime a pad when using a wax/sealant when a little bit goes a long way?
Anyhow, I think the OP has other issues regarding his DA/Plate/Pad setup. More info would be helpful.