Get a good footswitch -- one that has two separate switches that actuate at slightly different times just a few milliseconds apart. Wire the switch that closes first to the amplifier and the other one to the radio.
This way, the amplifier is turned on and ready just 5 - 10 msec before the radio can send any RF its way. It's a lot easier on just about any amplifier to be keyed like this rather than having the radio keyed first and then sticking the amplifier into the mix.
Yup. And the reason for this is the relays in the amp are always going to be hot switched when using an R.f. sniffer like CB amps.
Ham VHF amps eat relays too because they hot switch.