ive used both megs deep crystal step pre cleaner (step one) and scratch x, the precleaner isnt going to remove your swirls, it only preps paint to give the following steps a clean surface to hold onto... the scratch x should work if you're willing to put a lot of time and elbow grease into it... ive used the original version for this purpose on several cars, and it works great.. takes forever, but works. for me, scratch X 2.0 is worthless, they deffinatley upped the abrasiveness a TON, and it hasnt finnished down nicley for me yet, no matter how long you work it... mabye i just have a bad batch, but i cant reccoment scratch x 2.0.. perhaps someone else can, and possibly enlighten me as to how im using it wrong...
as for your LSP question... what is most important to you?, durability? looks? does it have to be available OTC? etc