It's hard to count 1234 while leading?
It's what you don't do! As long as you're aware of where beat 1 is, that's all you need. Tapping a foot, nodding a head, shrugging a shoulder.
If you have a metronome with a 'ding' available on beat one, set it.
Chords usually change on each bar, and often every four bars a new line will occur, so you should be aware of that. Presumably you're playing with a band, so get the drummer to do something special at the beginning of each line, which is probably where you'll end one phrase and start another. A splash cymbal for example.