there are few ways you can go about to finish it,
1, fit all the bolt-on parts,do all the bodywork, drill small guide holes at mounting holes on each panel, that way there will be no guessing during assembly, paint the engine bay if you have to get it running before paint, mask off the engine bay and paint the shell and all bolt-on parts off the car ,then assemble the car after wetsand and buff.
2,This is the way it should be done,if you want a best quality job, fit all the bolt-on parts,do all the bodywork, drill small guide holes at mounting holes on each panel, that way there will be no guessing during assembly, paint the shell and all bolt-on parts off the car ,then assemble the car after wetsand and buff.
3, fit all the bolt-on parts,do all the bodywork, paint the whole car,wetsand and buff,drop motor,interior and glass
Don't paint jambs first and paint the car later,alot of people may not agree with me as this may offend them, but that is not the right way to do a show car,atleast not to my standards, but if you like tape lines in jambs ,some dry areas around the edges and overspray, then it's all good