After you dry off the acetone completely, you can resuspend the proteins in PBS or any other phosphate buffer. However, there are other buffers you can use. Just make sure you do not exceed the maximum salt limit. See 'http://www.beyotime.com/Compatibility%20Chart%20For%20Bradford%20Kit.pdf'   for the maximum limits.

You can concentrate the proteín in cartigde and resuspended at original volume in buffer Tris-HCl, Phosphate, or any other buffer acording future protein charactherization analitical assays.

The buffer to be used depends on the further analysis you can to do. If you only want to measure protein concentration using Bradford method, then it's quite simple. You can use many buffers: phosphate buffer, carbonate buffer, Tris-HCl (cheap and easy to prepare)...If you want to do any other analysis to characterised your proteins, then you have to check which are the best physiological conditions for them in terms of salt concentration, pH, etc.

Please, be careful with protein extraction using TCA. TCA interferes with many reactives. After protein precipitation using TCA, you have to be sure that you completely remove TCA from the protein pellet (several washes must be done). Otherwise, TCA affects Bradford assay, sample buffer for electrophoresis etc.

PBS works well. However, If you think your further experiments can be influnced by introduction of salt, then I would suggest for partial rehydration  buffer (7 M urea, 2 M thiourea and 4% CHAPS)

Thanks for all the great suggestions. I am gonna try it out and see how it goes. 

Could I dissolve my TCA/DOC-precipitated protein sample in PBS for concentration measurement using BCA kit before analysing the samples using Western Blot?