If you want to double him with another CB, you'll have to put an extra one on. (ie. respond to 2 WR sets, with 3 CBs) The third CB should come in on the #1 WRs side of the field, and should double up (depending on what else is going on). Of course, when they go to 3 CBs, if you respond with 4, I think you'd end up doubling the #2 WR then. (With 4WR, the 5th CB is back on the #1 side.)
I have seen some teams double both the #1 WR and the #2 WR by going into a dime in any pass situation with the offense only having 2 WR, but I'm not convinced it works any better than just the regular man coverage + cover 2.
If you want to double him off the line with a safety, you'll have to go to a cover 0, but expect to get beat deep often, as the safeties may not pick the receiver you want them to.
