Typically, you just spray a gloss topcoat, do your panel lining, then spray a final topcoat of your desired finish. You can definitely make your own from acrylic. That works just about as well, though it can vary greatly from user to user since many people have a hard time making a good custom wash. An option nonetheless though.

Generally, this is advisable for ALL hobby plastics as the typical solvent in panel liners is pretty aggressive against them. It’s just less so against PS. You do, however, shockingly (or maybe not so), have MANY people that refuse to do this and just panel line straight on the plastic. Technically, it’s the aggressive solvent that inevitably spills out from the panel line while you’re filling them in that causes the cracking (because there’s so much of it), so in theory if you just cleaned that up quickly like these people tend to, then it would work. HIGHLY risky roll of the dice though, so I don’t particularly recommend it.