smoke when starting up ?

[N2AE86]

It would be more likley that its the valve stem seals rather than the guides themselves.  Mine does similar if left for a few days, got the seals just need to get enough time to swap them.

FYI you can also do it without using compressed air.  A long length of thick para cord, can be tucked down the spark plug hole (make sure you tie a fat knot in the end so you dont loose the whole thing down there) - then with the cam removed turn the engine over so you set the bore your working on to TDC - the piston will compress the cord against the bottom of the valves - holding them up.  Then you just need to compress the valve spring, remove the retainer and collets.  This tool from snap on makes life easier.

http://buy1.snapon.com/catalog/item.asp?P65=&tool=all&item_ID=78777&group_ID=1578&store=snapon-store&dir=catalog

To give you a better idea of how it works - its not a VW lump but you should get the gist.

http://www.aeu86.org/index/engine-diy-4age-valve-stem-seals_/cat/9/topic=4156/post=75407