Come on!  Sure if you don't wash off the offending oil then of course it is contagious, and will spread.  That is, after all, how you got the rash in the first place, is it not?  You came into contact with the urushiol oil, your body reacted to it, hence the oil is contagious.

  We already know that the oil is contagious but the real question is whether, or not, the liquid coming out of the blisters can reinfect, or infect someone else after all of the urushiol oil has been removed from the skin.  And the answer is, apparently, No.  There is no urushiol oil in the liquid that exits the blisters.  Since the urushiol oil is the contagious offender the liquid exiting the blisters is NOT contagious (mostly because it does not contain any of the urushiol oil). 

  Therefore, once you have properly cleaned all of the urushiol oil from your body.  And don't forget that the urushiol oil can remain on inanimate objects for up to 5-10 years, some studies suggest, you must wash all of the clothes, bed sheets, socks, shoes, shovels, underneath finger nails, animals and anything else that came into contact with the oil and wash them good!!  Some studies state that one should use Isopropyl alcohol (rubbing alcohol) first, then rinse, then soap, then rise and continue.  The urushiol oil is a resin like oil that is, apparently, very difficult to remove.  Once all this is done you should have only to deal with the allergic reaction. 

Hence, once all of the urushiol oil has been removed, from everything, then no amount of "rubbing can spread the rash".  But you can infect the rash and cause more problems than relief.  Now if you rub the rash with more urushiol oil then you will reinfect...

Regards,

Jeff.