Defense to Strong 1C

To defend against the strong 1-C opening

Overcaller bids even with fairly weak hand (6+HCP) to interfere as often as possible.
Dbl - shows clubs
One of suit = shows that suit
Three of suit = equivalent to a weak jump overcall
Two of a suit = shows that suit plus the next higher suit.
1NT = shows spades and diamonds (the pointed suits)
2NT = shows hearts and clubs (the rounded suits)

Defense to 1D response

Dbl = shows diamonds
All other bids the same as those for overcalling the 1C opening

responses to partner's overcall --

Suit bids are natural and non-forcing
Jump bids are natural and preemptive
1 or 2nt = one round forcing and game try - equivalent to a cue bid.

To show a good hand with opening value, bid at 2nd opportunity (passing the first time around)