I disagree. The use of TTimer is clean enough for me (except you don't use comprehensive object names, nor comments, nor documentation...).
Anyway, the use of messages and/or low-level components and APIs (i.e. "NewFormWndProc") is platform-dependant, so AFAIK there's no way to use them in a cross-platform way.
Windows GDI is way different than XWindow, which is different than GTK (even in same OS!), which is incompatible with Cocoa... That's why LCL sources are huge. They must encapsulate a lot of different stuff.